Due his lizard appearance, Shuichi Iguchi was a constant victim of racism. His early life was living among people who thought of him as a freak, trying to do anything about it was futile and he was filled with nothing but emptiness. However, after seeing Stain's last stand on T.V., he was influenced by Stain's ideology and formed a desire to change society to something better.
Three days after Stain's defeat, Spinner is seen smiling while putting on a mask similar to the Hero Killer's and brushing his hair back with his hands.
Spinner joins the other members of the Vanguard Action Squad as they look down at the camp where the students are staying. Later, once the invasion begins, he is seen grinning alongside Magne as Pixie-Bob lies on the ground, hurt and unconscious.
He then introduces himself and the other villains as the League of Villains' Vanguard Action Squad. Once Magne threatens to smash Pixie-Bob's face, Spinner tells Magne not to hurry and Tiger to calm down. He questions if Magne believes in Stain's ideals, and recognizes Tenya Iida as one of the people who brought about Stain's defeat. He then says his name and declares that he will be the one to make Stain's dream come true while revealing the enormous sword he had been carrying on his back. After Tiger reprimands him for scarring Pixie-Bob's face, he questions if heroes truly dream of finding ordinary happiness in life.
Spinner attacks Mandalay with his huge sword and she uses her Quirk to compliment him. The compliments make him blush and she is able to dodge his attack and scratch him with her cat gloves because of this. Spinner then insults her for using such a dirty trick on him. Before she can attack Spinner again, Magne uses her Quirk to pull Mandalay to her. Tora saves Mandalay and they start fighting each other.
While he is fighting Mandalay, his huge sword is destroyed by Izuku who used his Quirk to reach Mandalay as quickly as possible to tell her that Kota is okay. Mandalay continues to fight Spinner while Izuku starts to leave the battlefield. Magne, however, realizes that Izuku must be killed because he defeated Muscular; Magne starts to go after Izuku.
However, Magne cannot reach him because Spinner throws a knife between her and Izuku, thus stopping her from pursuing Izuku further. Magne scolds him for this action because Izuku is on the priority kill list of the Vanguard Action Squad. Spinner then clarifies that the list belongs to Tomura and tells Magne that Midoriya was the person that Stain saw fit to save thus being a man worthy of the title of a true hero. Mandalay uses this diversion to kick Spinner in the face.
Spinner is eventually overpowered and apprehended by Mandalay. Spinner curses the Pussycats and vows to fulfill Stain's mission. Kurogiri arrives and rescues Spinner and Magne, teleporting them back to the League of Villains' hideout.
After Katsuki and the League of Villains watch a video clip of U.A.'s public apology, Tomura understands why society is criticizing U.A. for their failure and that is because the current Hero society is not just. Spinner agrees that the current Hero society isn’t just since the modern Heroes are only doing their job for compensation and not out of selflessness. Tomura explains that the League of Villains are fighting for a just society and intends to win this battle.
Tomura orders Dabi to remove Katsuki’s restraints, although Dabi is unsure since Katsuki might attack; Tomura wants to treat Katsuki as an equal and is aware that Katsuki knows he has no possibility of winning. Dabi has Twice remove the restrains. As Twice removes the restrains, Mr. Compress apologizes to Katsuki for forcibly kidnapping him and explains that the League of Villains are not just a group of hoodlums perpetuating crimes nor did they casually abduct him; he goes on by saying that everyone in the League of Villains is shackled by the current society and hopes that Katsuki understands their discrimination.
Katsuki’s restraints are removed. As Tomura approaches, Katsuki attacks Tomura with his Explosions. Katsuki tells the League of Villains that it is pointless to try and make him change his mind as he has already been won over by the way All Might looks when he wins. Katsuki says that from the beginning he has dreamed of becoming a Hero and surpassing All Might and nothing they say will change that.
Out of nowhere, Nomu appear from a mysterious black liquid which takes the Pro Heroes off guard. Spinner along with the League of Villains are teleported by the mysterious black liquid to the League of Villains' destroyed warehouse where Sensei is.
After Katsuki is rescued by Izuku, Tenya, and Eijiro, Mr. Compress along with Magne and Spinner hatch a plan to recapture Katsuki. Magne magnetizes Mr. Compress and Spinner pushes him, causing Mr. Compress to fly at Izuku’s group. Suddenly, Mt. Lady uses Titan Cliff and intercepts Mr. Compress, which causes them to smash into each other, preventing Mr. Compress from getting to the students. Magne and Spinner prepare to throw Twice, but Gran Torino blitzes them causing them to become unconscious.
The unconscious Spinner along with Tomura and the Vanguard Action Squad are forcefully magnetized by Magne's Quirk courtesy of All For One; Spinner is sucked into Kurogiri's Warp Gate and teleported away.
Following Overhaul's defeat, the League of Villains seek revenge against Yakuza boss and attack the police who are transporting him. Spinner is handling the driving with Tomura, Dabi, and Mr. Compress on board. Dabi tells Spinner to stop swerving and drive better to which the latter takes offense to saying that he learned how to drive from playing video games like Grand Theft Auto.
Spinner then questions how attacking the police helps with creating a true hero society and whether they are actually following Stain's will. Tomura Shigaraki reassures Shuichi that it is a necessary sacrifice.
Less than a month before the Hero Billboard Chart JP, the League of Villains is in a sorry state. They're barely scraping by with no funds and have resorted to stealing from other criminal groups. After attacking the Creature Rejection Clan and not getting anything of true value, the League returns to their worn-down hideout. Due to his lack of successes, an irritated Spinner questions Tomura how long the League will live in filth. Tomura simply replies until they find All For One's personal Doctor. The rest of the teammates do not seem to care about their situation, but Spinner becomes increasingly frustrated and begins to lose patience,
Finally he begins to shout at Tomura, questioning him what direction the League's aiming for and what his plans are. Spinner points out the only reason he joined the League was due to Stain's ideology and his desire to change society, but the League of Villains aren't going anywhere. Before Tomura can give a clear answer, great rumbling shakes the hideout.
Tomura and his allies immediately evacuate the crumbling building and discover Gigantomachia, who asking for All For One's successor. He claims he devotes himself to All For One and challenges the League to see whether they are worthy of his loyalty. The League of Villains is easily overpowered and Gigantomachia begins to wail and cry, dismayed at their performance, tearfully crying out that Tomura's too weak to be a successor. A familiar voice echoes from the radio and Tomura realizes it's All For One's doctor.
Before the Gigantomachia can kill them by accident due to his frustration, the League of Villains is warped to the secret laboratory of the doctor, who introduces himself under the alias of Daruma Ujiko. Tomura and the League receives criticism and reproaches from Daruma, due to his lack of achievements and progress since the fall of All For One. Then, he asks Tomura what he and his band of young villains plan on showing him.
The answer finally makes Spinner understand that Tomura does not follow Stain's ideals. Tomura confesses that he felt empty before meeting All For One. The fragments of his past are buried inside a hole in Tomura's heart that acts as an endless source of rage. Tomura believes that no matter what, he will always have this weight on his heart and that's why he hates everything, and why he wants to destroy everything. Tomura tells that he will show Daruma heaven and hell if he will help.
Entertained, Doctor Ujiko agrees to help make Tomura's childish dreams come true, but still believes the League is weak and they need to prove themselves. They will not receive his full support until Tomura gets Gigantomachia to submit. This conversation causes Tomura to develop more determination to reach his goals, and after one adjustments to a small Nomu, Daruma returns them to Gigantomachia. The second confrontation starts.
In mid-December, after a month and a half of first making contact with Daruma Ujiko and Gigantomachia, The League is still fighting to get the giant to submit. Tomura is Gigantomachia's main target and doesn't care that other members, who take turns assisting Tomura in battle, having few hours of rest.
On their way to meet with the other members, Spinner reflects on how the League no longer aligns with Stain's ideals. He questions Himiko on why she is still with the League. She responds that she still loves Stain, Izuku Midoriya, and Ochaco Uraraka too and that she wants to 'become' them. Spinner notes how carefree she is. When they come across Tomura, Spinner notes how his eyes still possessed the look of a determined boy chasing after his dreams.
At that time, the League receives a sudden call from Giran, but it turns out to be someone else entirely. The voice on the phone introduces himself as Re-Destro, Grand Commander of the Meta Liberation Army. Re-Destro explains that they have Giran alive, that his army is made up of thousands of soldiers, that thanks to their satellite they have already located the position of the League, and that they have the power and the influence to mobilize the heroes against them. Spinner is shocked by Re-Destro's claims.
Re-Destro wants the revolution that changes society to be led by the Liberation Army but the League's popularity is interfering, therefore must be eliminated. As a declaration of war, Re-Destro gives Tomura the choice to bring the League to Deika City in Aichi Prefecture to face the Meta Liberation Army and be destroyed, or do nothing and be captured by the heroes when he gives their location.
When Tomura states his intention of confronting the Meta Liberation Army, Spinner states his worry about facing an army they know nothing about outnumbered only to learn that Tomura's intention was to lure Gigantomachia to the Army and make them weaken him. After they Warp to Deika City, The League is confronted by the Hero Slidin' Go who takes the League to the center of the city to begin the Revival Celebration.
While fighting the Meta Liberation Army, Spinner notices Tomura's Quirk being transmitted to things he hadn't touched.
As Tomura and Spinner continue towards the tower, Tomura asks Spinner if they still should've waited before confronting the Army with Spinner replying that even if they hadn't come, the Army would've still reported them to the Heroes and that the League was screwed either way. After getting overrun with the arrival of Twice's clones, Spinner shifts his attention to Koku Hanabata.
Spinner deduces the power Trumpet and the rest of the higher ups possess after hearing him announce Curious's death to their followers in order to motivate them to continue fighting. Deciding to take him out to lessen Tomura's burden. However, Trumpet declares that Spinner will never accomplish anything with his weak Quirk and 'hikikomori' lifestyle. Spinner states retorts that while he has nothing to love like Himiko does, he wants to ensure Tomura's future comes to pass, while also yelling that the Meta Liberation Army can't do anything without latching on to someone else similar to himself.
With help from Twice, Spinner finally latches on to Trumpet's truck. He then sees Tomura destroy a huge chunk of Deika City with his Quirk and Re-Destro admit defeat to him, while also stating the Meta Liberation Army was now under Tomura's command. Spinner was amazed and mentally notes the 'utterly destroyed horizon' looked beautiful.
Spinner later ate sushi with his comrades after the battle, asking Dabi if he would like some and noting Twice's mental condition seemingly getting worse. During Re-Destro's speech, Himiko asks him on Tomura still having one of his signature hands and he tells her one hand survived. He and the rest of the League came on stage when Tomura announced the Meta Liberation Army and League of Villains will become the Paranormal Liberation Front (which Spinner and Re-Destro coined together), becoming one of its Lieutenants. After the speech, he wonders aloud how Re-Destro is a CEO because of his now submissive attitude to Tomura. Spinner is surprised when Tomura collapses from his injuries, though is fine for the most part.