Naoya Zenin/Synopsis

History

During his childhood Naoya believed that Toji Zenin, his cousin and a member of his clan was weak due to having no curse energy. Once he went to visit him to mock him for having no curse energy, but was instantly surprised and was able to recognise Toji's strength in spite of lack of curse energy. This led Naoya to embrace the ideology that sin of the insignificant is the ignorance of true strength.

Itadori's Extermination Arc
After the Shibuya Incident, Naoya was called to stay by Naobito's side along with Ogi Zenin and Jinichi Zenin. On the way there, he made misogynistic comments towards Maki and Mai, claiming that Maki does not deserve to live and Mai is much more acceptable for the Zenin clan.

When Naoya met Ogi and Jinichi, he stated that he would become the new clan leader, insulting his brothers and Jinichi in the process. After a short scuffle, Furudate walks out of Naobito's room and announces the clan leader's passing. The short man then read Naobito's will, revealing that, in the case of Satoru Gojo's disappearance, Megumi Fushiguro is to become the next clan leader. This fact angers Naoya, which is enough for him to head to Shibuya and attempt to hunt both Sukuna's vessel and Megumi down, killing two birds with one stone.

He arrives shortly after, finding Yuji with Choso as they were exorcising curses. Naoya is initially disappointed that Megumi is not there, but he quickly attacks both Yuji and Choso. However, the fight is interrupted by the arrival of Yuta Okkotsu. Naoya notices his immense presence, immediately presenting himself as an ally and asking Yuta not to tell anyone else that he was here.

Naoya makes use of the situation and attacks Choso as Yuta chases after Yuji. During the initial scuffle, he comments that he knows about Blood Manipulation and Choso has no way of winning. The fight is taken into an underground passage, where Naoya seemingly overpowers Choso. The curse-human attempts to use Flowing Red Scale: Stack to turn the tables, but the Zenin family member manages to counter by stabbing Choso and hoping he bleeds out. After that sneak attack, Naoya makes an off-handed comment about his brothers which prompts Choso to talk about the value of brotherly bonds.

Choso then makes use of the fact he's half-curse and launches his blood towards Naoya in a giant wave. The Zenin family member attempts to dodge, but some blood eventually gets on his clothes and Choso then defeats him with Supernova, managing to poison him with his blood in the process. Before Choso could finish his opponent off, Yuta arrives and knocks the curse-human out. Okkotsu, who carries Yuji's unconscious body behind him, then comments that Naoya looks hurt.

Naoya feels insulted by Yuta staring down at him, but a sudden pain causes him to vomit. The Zenin family member is bewildered, not understanding right away why his body reacted this way. As he understands that Choso must not have been human, Yuta offers to heal him in exchange for informing the higher-ups of Itadori's death. Naoya presumably accepted the deal and left Shibuya.

Perfect Preparation Arc
When Maki arrives at the Zenin household, Naoya immediately insults Maki about her burnt face. Maki counters this by saying that she thought Naoya judged women by their butts instead of the face. Naoya ignores her and tells her to answer his question. He adds on that Maki is unable to use cursed techniques, nor see cursed spirits. He also says that her face was all she had before it was ruined, Naoya adds that he's been lonely lately asks Maki if he should bully her like he used to in the past. Maki ignores this as Naoya asks her if she's going to follow Megumi Fushiguro and Yuta Okkotsu like a lap dog.

Now in a different room, Naoya talks to Jinichi as he says he's too reckless and that Megumi is the better choice. While the two are chatting, the alarm sounds as Naoya wonders why there's so much noise. Ranta who suddenly rushes in informs the two that Maki has gone mad and also has killed Ogi. He adds on that the Kukuru unit has also been deployed to go after Maki. Naoya thinks to himself is surprised that Maki managed to kill Ogi.

After both the Kukuru and Hei units are slaughtered by Maki, Naoya arrives and confronts her after she throws Jinichi's head into the water, asking if she has a human heart. Maki responds by saying she no longer has a heart as it was taken from her.

Naoya immediately attacks Maki with a barrage of punches who's able to block all of them. Naoya manages to grab Maki's arm and uses Projection Sorcery on her which traps her within a frame, he then kicks her out of the frame which sends her flying. He thinks to himself of how Maki isn't Toji and that he is.

He continues attacking Maki who's unable to fight back. Naoya decides to use his speed to try and pierce Maki, however, much to his surprise, Maki prepares to use Shiranui-Gata. Instead of directly attacking Maki, Naoya slaps her and gets behind her preparing to attack. However, Maki surprises him and slams him into the ground, leaving him bleeding and wounded.

After Maki leaves, Naoya tries to crawl to safety, gloating to himself that she didn't finish him off. However, Maki's mother, who was also on the verge of death, walked up to Naoya from behind and stabbed him in the back. At this point Naoya was too weak to use cursed energy to defend himself, so he was killed without putting up a fight.

Culling Game Arc
Being that Maki's mother didn't use cursed energy to kill Naoya, he was able to reform as a Vengeful Cursed Spirit. While Maki and Noritoshi are making their way through the Sakurajima Colony, Naoya enters. After a momentary pause, he attempts to stutter out Maki's name, then rockets into her with far greater speed than either she or Noritoshi can react to. Maki survives his assault, relatively unscathed, and tries to hit him back. He dodges using his technique, reminding Maki of how he moved as a human. However, Maki isn't aware of his true identity yet. Before she can try attacking again, Naoya strikes her up against another wall. He then reveals a grotesque, twisted face, heavily reminiscent of the one he had in life, and manages to fully say Maki's name, confirming his identity to her. As the two continue to fight Naoya metamorphosizes into an evolved cursed form and begins to overpower Noritoshi and Maki with his speed, eventually reaching a speed of Mach 3 and pins Maki down. Naoya briefly mocks Maki or the death of Mai before being attacked by Noritoshi, as he engages he begins to overpower Noritoshi almost killing him before being interrupted by Hagane Daido and Rokujushi Miyo. The two assist Maki and Noritoshi in fighting Naoya until he decides to activate his Domain, inside the Domain he manages to incapacitate Rokujushi and Hagane and about to kill them before Maki stabs Naoya in the chest revealing she is unaffected by the Domain due to having no cursed energy, she delivers the finishing blow Exorcising Naoya for good.