U.A. High School
Shota and Present Mic used to be classmates at U.A. High School and were good friends for a very long time. Present Mic even came up with the hero name "Eraser Head" for Shota. Although he used it as an example of why his class should be careful about choosing a hero name as they could be stuck with a bad one forever, he doesn't seem to mind the name Mic picked for him.
They have contrasting personalities, with Shota being calm and composed while Mic is very excitable and energetic, but they still get along very well, unlike him and All Might.
Due to their contrasting personalities and the way Shota antagonized Izuku on the first day of school, he and All Might initially did not get along. All Might disapproves of Shota's overly-strict teaching methods while Shota dislikes the favoritism that All Might shows Izuku.
However, Shota respects his fellow hero who shows him the same as seen when he saved Shota from Nomu in U.S.J. Arc. After the Hideout Raid Arc, when All Might defeats All For One and loses One For All, Shota tries to reach out to him by inviting him to get a drink sometime, hinting that the two have found a level of understanding. All Might kindly turned him down but offered him a drink after they met the wild Bakugo Family. Shota even told him to take it easy and recover now that he is retired.
They are both fellow pro heroes and homeroom teachers of the Department of Heroes for their respective classes. As Vlad King views Class 1-A as his class’ rivals, this rivalry is extended toward Shota, with Vlad acting out competitively towards him.
Despite this rivalry, Vlad knows when to cooperate with Shota during serious moments. This was shown in their meeting with the media where he was worried that Shota would lose his temper though was surprised when the latter kept calm and agreed with the heckling.
Nemuri was Shota's senior when he was a U.A. student. When he was in the second year, she helped him to carry out his Hero Work-Studies with the hero His Purple Highness, forming the Team Purple Revolution together with Oboro Shirakumo.
Since then, he and Nemuri appear on good terms and they often help each other, like when he ask her to help his class in matters he couldn't be bothered with. They usually have a good relationship, and Shota doesn't bother with Nemuri's "enthusiastic" attitude towards youth, but he is annoyed when she makes decisions for him without his consent.
This behavior is the main reason why Shota is a member of the U.A. teaching staff. When Nemuri was personally requested by principal Nezu for the position of teacher, she submitted a recommendation to the principal for Shota, being accepted as a teacher, even though he had told her that the idea of him being a teacher is the epitome of irrationality.
As the homeroom teacher of U.A.'s Class 1-A, Shota cares a lot about the safety and well-being of his students, willing to sacrifice his own life to protect them from danger. He has very high standards for his students when it comes to heroism, and seriously pushes them in that regard. Although he rarely gives praise, he expects great things from all of them and he knows how to recognize when they do a good job.
However, he is also extremely strict, and does not hesitate to criticize and scold them when they do not meet their expectations or make bad decisions, never pulls his punches with the truth, especially when it comes to pointing out flaws or naivete. His stern demeanor also make it hard for his students to determine whether or not he is being sincere in his teaching methods, so when he threatens them with "rational falsehoods" like expulsions or punishments to force them to exert themselves to the fullest, they mistake him for being serious and understandably get scared.
When Shota first meets Izuku, he had zero faith in Izuku's ability to be a hero and intends to ‘expel’ him on the first day of school. Izuku was as equally put off by him, until he realizes who Shota is and becomes the first of the class to identify him as Eraser Head. Shota takes note of All Might's interest in Izuku, as a result he considers him just as reckless as the latter. However, when Izuku proves his worth to Shota, he acknowledges that Izuku has the potential to become a hero if he can learn to control his Quirk.
As the series goes on, Shota continues to regard Izuku as a "problem child" due to Izuku's habit of causing trouble and getting himself into danger. However, Shota also shows faith in Izuku's potential and is amazed at his growth and the improvement in his abilities. He has recently started to respect Izuku more often, though is still strict on him.
In return, Izuku respected Shota's work as a hero and expressed concern for him when he fought the League of Villains and was amazed by the latter's abilities, since he realized he underestimated him. However, he was horrified to watch him being defeated by Nomu and carried Shota away.
Recently, Shota has taken note of Izuku's Quirk gradually changing and asking him on the phenomenon and gets a vague answer.
Like with Izuku, Shota is rude to Katsuki due to the latter's brash and violent behavior. He tends to look over Katsuki more than any other student, stemming his reckless and loud behavior.
During the Final Exams Arc, he overheard Katsuki's declaration to the class and noted he was getting worse. Shota also paired Katsuki up with Izuku for them to work together and it worked.
However, he acknowledges he has the qualities of a hero when asked by the press about his "villain like" behavior.
When he meets the Bakugo Family, he was complimented for seeing Katsuki for who he really was and not overlooking his faults.
During Joint Training Arc, Shota complimented Katsuki's willingness to cooperate with his team, which led to his victory. Shota expressed pride in Katsuki gradually changing his ways while Katsuki told him to not dwell on it.
His relationship with Shoto is good. Generally, he does not cause him as many problems as Izuku and Katsuki, although Shota knows that Shoto also has his own issues to overcome.
During the practical exam, Shoto was paired with Momo, while Shota was their opponent. During the confrontation, Shota manages to wrap up Shoto. He tells Shoto his plan placed too much of the burden on himself and that he needs to trust Momo more. Shoto follows the advice of his teacher, and together with Momo they manage to defeat him.
Days later, during the Hideout Raid Arc, Shoto was one of the five students who skipped the rules to go to rescue of Katsuki. This action brought him harsh criticism from Shota who said that, had it not been for All Might's retirement, he would have been expelled along with the other students.
Over time, their relationship improves. Shota showed concern for Shoto when the fight between Endeavor and High-End was broadcast on television. When Endeavor appeared on the verge of defeat, Shota ran to where Shoto was, concerned about how this could affect him. After Endeavor's victory, he stood over him as he clasped his hands in prayer, relieved his father emerged victorious .
His relationship with Ochaco does not go beyond that of professor / student. As her teacher, Shota tries to teach Ochaco to be a heroine, not hesitating to criticize her harshly when he sees that her performance is not adequate, as when she barely passed her final exam against Thirteen.
Likewise, he also tries to encourage and comfort her in difficult times. After Sir Nighteye's death, Ochaco feels guilty because he thought he could have done much more to save him, but Shota consoles her and reply that she bears no responsibility and the fault lies with the Heroes, asking her to take time and think about what she wants to do in the future, to which she responds that she wants to save people.
Shota is aware of Minoru's perverted personality, he even does not hesitate to describe him as the "embodiment of lust". Although Aizawa does not do much to correct this attitude, he does not allow Mineta to cross certain lines of human decency, especially when it comes to peek on girls while they bathe. For this reason, Shota usually warns other people about Minoru’s attitude so that they take the necessary measures in this regard, or he generates an aura of intimidation to make sure that Mineta does not do anything perverted.
However, Shota also supports him and gives him confidence when he feels overwhelmed by a challenge, as when Minoru was nervous about the Provisional Hero License Exam. Shota encourages him to do his best so that he can pass the exam and further his goal in becoming a Hero. This both scared and encourages the boy to trying his best. 
In spite of him teaching his rival class, Neito doesn't show any ill will to the teacher and shows him respect. Despite this, Shota has shown to find annoyance in Neito's behavior, as he scolds him before Itsuka can and tells him to behave.
It’s been implied that Shota initially noticed of Hitoshi during the U.A. Sports Festival, because of the similarities in their Quirks’ lack of real combat efficiency. Shota later decides to mentor Hitoshi personally to help him transfer into the Hero Course, passing on his Capturing Weapon techniques to Hitoshi to increase his battle efficiency.
They share a student-teacher relationship in a manner similar to Izuku and All Might with the same sentiments as Izuku after the latter passed his entry into the Hero Course.
Present Mic suggests that one of the reasons of his interest for Shinsho is because Aizawa sees his young self in him.
Until the Shie Hassaikai raid, there was little interaction between the two. Mirio respects him as a teacher, and Shota recognizes Mirio as U.A.'s most powerful student, even considering him to be the top candidate for No. 1 Hero over all of the Pro Heroes.
After the rescue of Eri, the loss of Mirio’s Permeation Quirk and the death of Sir Nighteye, Shota comforts a disconsolate Mirio, promising that he will look for a way to help him to recover his Quirk.
When Eri is under Shota's custody, Mirio helps him take care of her and it is common to see them together when Eri walks through the U.A. Shota is hopeful that Eri will learn to control her Rewind and thereby, restore Mirio's Permeation.
Alongside Hizashi, Oboro was one of his closets friends when he was still a student at the U.A. High School. They had a good relationship and used to interact frequently, especially after the second year, when Shota began to have serious doubts about his abilities and his future as a hero. Oboro was there to encourage him and help him with his problems. Oboro used to tell Shota that the only thing he achieved with his negative attitude was to psyching himself. Oboro really thought he was better than he thought, and if he intended, he could do anything.
Thanks to Nemuri, both did their Hero Work-Studies at the Purple Revolution Agency, where they show an extraordinary teamwork to deal with the villains. It was at one of those moments when Oboro lent his goggles to Shota so that he could protect his eyes and thus, face a villain whose Quirk countered his Erasure.
Oboro highly valued his friendship with Shota and Hizashi, and even proposed to them the idea that, once they graduated, the three together would create and organize their own Hero Agency. Unfortunately, a week later Oboro died after being crushed by a pile of rubble in a confrontation against a villain, who was defeated by Shota alone. During the fight, Shota heard how his friend was always cheering him on, but after his victory, he founds out that Oboro was already dead before he started fighting, and Sensoji tells him it was likely he was giving himself a pep talk and the stress situation made him imagine it was Oboro. Shota, along with Hizashi, mourned the loss of his friend.
Even today, despite the years that have passed, Shota still remembers her former classmate. Present Mic suggests that one of the reasons for his interest in Shinsho, apart from seeing his young self in him, is also because of Shirakumo. 
Shota is terribly affected when Detective Naomasa and Gran Torino inform him that All For One stole and desecrated the corpse of Oboro Shirakumo, subjecting his body to several modifications and using as the base to create the Nomu Kurogiri.
Sensoji was a student of class B with whom he did not get along. He had an arrogant personality, and he used to despise Shota by considering him a weakling and having an equally weak Quirk. Although Shota did not usually consider him a smart one, and he generally ignored his provocations, since at that time he was going through a crisis, having serious doubts about his ability to be a hero, he could not deny that there was a certain truth in his words.
However, thanks to Oboro's support, Shota improved his combat ability, and during a school training, between him and Oboro they managed to defeat Sensoji. Still, Shota did not consider it a fair fight, arguing that a two-on-one is not fair, and tried to have the fight end in good terms between the two, but Sensoji considered his defeat to Aizawa humiliating, and despised his mercy.
Despite this enmity, when Shota defeated Garvey alone, Sensoji did not hesitate to congratulate him and acknowledge that he had accomplished an outstanding feat, and that he should be proud of it. After this incident, their relationship improved a lot. Sensoji no longer antagonized Shota neither got angry when Shota defeated him in training battle, and even thanked him for his advice.
Shota has known Ms. Joke for a long time; their workplaces were once close to each other and as a result whenever there was trouble, they would assist each other. Ms. Joke often states she likes him and enjoys poking fun at him, though he seems to find her jokes and general disposition to be annoying, but still tolerates her presence and shows a willingness to work with her.
Ms. Joke is determined to get Shota to laugh using her Quirk, Outburst, or otherwise, however, Shota is often one step ahead before she gets the chance by erasing her Quirk.
His Purple Highness was the hero whose under guardianship Shota took part in the Work-Studies. Mr. Purple highly valued Shota's ability to be a hero and congratulated him when he did a good job, but he was quick to recognize that Shota Aizawa is not exactly a people-person and would make for a poor media presence.
Mr. Purple is the one who teaches him the importance of showing a smile, even if things are not going well, in order to convey tranquility and confidence to the people he should help.
CiviliansOverhaul, causing Izuku visible pain. Shota, albeit injured, was brought to the scene so he could erase Eri's out-of-control Quirk. Since then, Shota has been somewhat of a guardian for Eri, sometimes taking charge of her care as she lives with the U.A. faculty in the dorms. Eri is comfortable with Shota's presence and listens to him well.
Shota appears to have a soft spot for Eri, having bought her a matching set of cat-themed clothes while she was in the hospital for her to wear when she was discharged. Shota is known to like cats, making this gesture somewhat more meaningful.
They first meet in the U.S.J., when Tomura leads a raid in the hopes to kill the symbol of peace. Eraser Head began to fight off Tomura's grunts before Tomura attacked him while Shota was thinking he was the "final boss". However, Tomura's attack leaving him with a destroyed elbow after he deduces and exploits the hero's weakness though Tomura still shows him respect and calls him cool for not only still standing but standing against him and his forces single handedly.
Unfortunately, Tomura's attack left Shota blind to notice Nomu thrashes the pro-hero into the ground, something Tomura watched with glee. After Tomura makes a move to kill his students, Eraser Head quickly prevents this by canceling out his Quirk and Tomura is forced to compliment him on his strong will before Nomu takes him down.
Because of Shota's Quirk, Kai took an interest in the latter and had him captured for experiments. However, thanks to the intervention of heroes and his students, Shota was saved.
Shota met the villain Kurogiri at the same time as Tomura Shigaraki. At that time he saw him as one more criminal, a member of the League of Villain. However, he recognized him as one of the most dangerous after he had stopped the class from escaping and trapping them inside the USJ hall.
All this changes when he and Hizashi are informed that Kurogiri is their former class mate and friend Oboro Shirakumo, or more correctly, his corpse revived and bioengineered by All For One. The idea that the body of Oboro has been desecrated in such a way leaves him feeling agitated, and he hopes that everything is just a big misunderstanding, because when they fought at U.S.J., Kurogiri's behavior was completely different from Oboro's.
Due the Nomu's ability to retain personality traits of their past life, Naomasa and Gran Torino plan to try to wake up Oboro with some attachments he had toward his old life, making Shota and Hizashi personally interview him. The villain does not react to seeing them and does not seem to remember anything when he was Oboro, but his genuine concern for others (in his case Tomura Shigaraki) and the fact that he describes himself as the type of person who cannot abandon others, confirms Shota that he is really his friend Oboro.
Shota meets Knuckleduster while the latter assaulted Mario Kugutsu trying to make him spill the beans about Trigger. Thinking that he was part of the "spontaneous villain" outbreak, Shota tries to stop Knuckleduster, but he responds violently starting a fight between the two. Shota tries to use his Quirk to stop him, surprised to see that it did not work on him, but soon realizes that Knuckleduster is Quirkless.
Understanding this, Shota stops fighting Knuckleduster and apologizes him because if he isn't using a Quirk for illegal activities, then he falls outside hero jurisdiction. He thinks about calling the police to take care of him, but when Mario, Soga Kugizaki and his friends become Instant Villains, he helps Knuckleduster to stop them.
Later, Shota thanks Knuckleduster for his assistance though warns him about the dangers of his vigilante activities. Knuckleduster replies that Heroes need people like him to deliver justice without restrictions. Shota finds it a ridiculous notion that Knuckleduster believes his unlawful justice are crimes of conscience and finds him to be a troublesome old man but respects his integrity.
They do not meet again in person until several months later, while he is investigating Trigger's traffic. Koichi meets Aizawa by chance, and both recognize each other from their previous encounter. At that time, the Next-Level Villains Octoid was on a rampage, so Shota tries to stop him, but is wounded in the fight. When Octoid was about to finish him, Koichi intervenes to save his life. With the help of the Hotta Brothers, Shota and Koichi collaborate to defeat Octoid.
After that confrontation, every time Koichi meets Shota, he greets him friendly, although Aizawa prefers to ignore him.
The Hotta Brothers
At first, Shota had a confrontation with Jiro and Ichiro Hotta, while investigating the traffic of Trigger. They attack him, but Shota defeats them easily. The Hotta Brothers avoid being arrested for their illicit dealings by becoming Shota's associates. Since then, Shota uses their store as his impromptu hideout, which frustrates the brothers to no end, and they do not hesitate to protest to him for this. Shota does not care about their opinions about him (although he admits they make good coffee).
Still, they do not hesitate to lending him a hand in the fight with Octoid.