Twice respects Tomura as the leader of the League of Villains, and tends to obey most of his commands. This is evident during the Shie Hassaikai Arc, per Tomura's order for Himiko Toga and Twice to temporarily join the Yakuza. At first, Twice refuses to assist Overhaul and the Shie Hassaikai due to what they had done to Mr. Compress and Magne and feeling guilty about it.
He begs Tomura not to let him go. Tomura takes off his mask revealing a calm, decided face. He tells Twice that he's going to help Overhaul for him, himself, and the rest of the League while noting that he knew the Shie Hassaikai were never interested in being equals but wanted to undermine the League. Tomura recalls when Twice said someone will pay for Magne's death and says that helping Overhaul is one way and that he believes in Twice.
These words inspire Twice to be himself and do his best during his time as a Yakuza which inadvertently leads him, along with Himiko, to 'run amok' as Overhaul had feared. In being himself, Twice manages to obtain the revenge he wished for.
Vanguard Action Squad
Dabi is shown to have no problem working with Twice and seemingly not annoyed by his antics and contradictory personality. In return, Twice has confidence in Dabi's strength and rebuffs his doubt about his own strength. It is implied that Twice and Dabi view each other as brothers in combat.
However, there may be arguments between the two, given that Dabi does not care what happens to his fellow League members, which conflicts with Twice's strong sense of camaraderie. When Giran was kidnapped by the Meta Liberation Army, Dabi does not hesitate to consider it nonsense to go and rescue him, which generates a violent response from Twice.
When Twice is cornered by Hawks, Dabi thinks to himself that Twice shouldn't blame himself and the scummy heroes are to blame as always. Another note is that Dabi even gave Twice some encouragement to keep fighting, showing no signs of blame towards his comrade, and actually gives Twice a high-five. Upon witnessing Twice's death at the hands of Hawks, Dabi appeared devastated to the point where he fully committed his task to killing Hawks to avenge his ally, but only because he cared more about Twice's worth to his own ambitions than his friendship with him.
Twice and Himiko are shown to get along well. During their internship in the Yakuza organization, Himiko shows a great understanding of Twice's feelings about them working together with the Yakuza. After his masks rips during a confrontation with Sir Nighteye, to show half of his face, Twice begins to split. Himiko repairs his mask with a handkerchief and reminds him that if they don't cooperate they will never get the chance to get revenge for Magne. 
The two decide to 'do things their way' which results in them sabotaging the Yakuza's plans by angering Mimic to losing his concentration leading to his capture as well as leading Ryuko's squad to aid in the battle against Overhaul.
The sympathy shown to him by Himiko during their time as Yakuza causes Twice to care for her. He calls her his soulmate after she repairs his mask with a handkerchief. Twice later questions if he can have a kiss as they look for an exit out from the underground paths. He also dresses her in the fake jewelry stolen from the Creature Rejection Clan. 
During the battle against the Meta Liberation Army, Twice finds the unconscious and grievously-wounded Himiko after her fight with Curious. This causes him a personality conflict until his "good" side prevails and he bursts out in tears, telling how much he cares about her and the League of Villains as they gave him a place to belong, and showing he treasures the handkerchief she used to replace his ripped mask back in the Shie Hassakai base.
His desire to save her life is so strong that, after overcoming his trauma and creating an army of Doubles of himself, Twice protects her from the Skeptic puppets, and later he creates a Double of her to give her a blood transfusion. When the battle begins to worsen, he takes her away from the danger. One week after the Revival Celebration, after the League and the Army decided to ally forming the Paranormal Liberation Front, Twice mourns over Himiko Toga’s Double death, which annoys the real Himiko, who is alive.
Upon his death at the hands of Keigo Takami, Himiko was left deeply hurt and devastated upon holding and hearing Jin's final double clone as it melted after hearing his final good-bye to her and his friends. This led to Himiko going on a violent-omnicidal/suicidal rampage slashing and slaughtering mass numbers of Heroes out of rage after his death that later further strengthened her conviction to make a world where the only things in the world were the things she loves and everything and everyone else is destroyed and slaughtered in memory of Jin.
Twice became indirectly responsible for Magne's death when he brought Overhaul to the League. Twice felt remorseful for Magne's death at the hands of Overhaul and vowed revenge. He got visibly angry when she was misgendered by Overhaul.
Twice feels responsible for Mr. Compress losing his arm at the hands to Overhaul. Twice vows to get revenge for what Overhaul did to Mr. Compress and Magne.
Twice grew to be rather close with Hawks once he became part of the Paranormal Liberation Army. He was impressed by the hero's work spreading the beliefs of the Liberation Army and later asked him to tutor him about the book, Meta Liberation War. Twice came to ask him for advice on the hero's definition of the ideology of liberation, openly telling Hawks that he was a good guy. The villain took pity over Hawks' reason for joining the Liberation Army, since he wanted to live in a world where he could be free, and tells the hero they will fly as high as they want together.
When Hawks revealed his true allegiance, Twice was deeply hurt by this betrayal, viewing it as another result of his carelessness when he brought Kai Chisaki to the League and got Magne killed, and because of his decision to place his trust in Hawks, it jeopardized the Paranormal Liberation Army. Acting on rage and sadness, Twice attacked the Hero, despite his plea to stop.
He is later killed by Hawks, making him the first Villain to be directly killed by a professional Hero.
Twice thinks Giran is a 'swell and wonderful guy' and likes that he's been looking out for him since joining the League. When it is revealed that Giran is captured by Re-Destro and his Meta Liberation Army Twice becomes angered and demands Giran's location and safety. Twice felt relieved when he found Giran alive despite the injuries and managed to escort him to safety upon the destruction of Re-Destro's tower at the hands of Tomura.
Initially, Twice is impressed by Overhaul's display against Team Reservoir Dogs and decides to recruit him for the League of Villains. However, his impression of Overhaul changes drastically when Overhaul kills Magne and destroys Mr. Compress's arm in Overhaul's first meeting with the League. Twice holds a grudge against Overhaul for this and wishes for revenge.
When Tomura tells him that he and Himiko will work for Overhaul he refuses. Twice then begins to exhibit signs of 'splitting' and admits his feelings of guilt for allowing Overhaul to harm the League.
At the Shie Hassaikai Compound, he admits to not liking any of the Yakuzas and refuses to tell them anything regarding his Quirk. However, Shin Nemoto is able to get him and Himiko to reveal their Quirks. When Overhaul refers to Magne as 'he', Twice erupts and corrects him and also reminds him that it was his second offense.
During the raid on the Shie Hassaikai Compound Overhaul orders him and Himiko to hold off the enemy to cover his escape. They reluctantly obey. Frustrated, Twice calls the Yakuzas useless as his Double of Kendo Rappa is quickly taken out by the Sir Nighteye. Later, Twice and Himiko decide to do things their way resulting in sabotaging Overhaul's plans. When Himiko confesses, while they make an exit, that she wants to see Overhaul suffer, Twice comes up with the plan to lead Ryuko's squad to Izuku's and Overhaul's battle. He also tries to get a clone of Mr. Compress to capture Eri but the copy refuses to partake in the battle.