Kokichi Muta/Synopsis

Kyoto Goodwill Event Arc
Mechamaru arrives at the Tokyo College for the Kyoto Goodwill Event, along with the other Kyoto College students and teachers. When the Kyoto students notice the Tokyo students, he talks with the others about how Yuta Okkotsu is not there. Mechamaru is there when Satoru Gojo arrives and reveals that Sukuna's vessel, Yuji Itadori, is alive.

Later, Mechamaru attends the pre-event meeting with the other Kyoto students and principal Yoshinobu. As Yoshinobu instructs them to kill Yuji, Aoi Todo gets annoyed by this and leaves after threatening them all. Mechamaru then talks with the other about what to do with Yuji and Aoi. Mechamaru also has concerns about Toge Inumaki, to which Noritoshi Kamo says that Toge will not be a problem.

When the events begins, Mechamaru along with the other Kyoto student head towards where Yuji is at. When Yuji is separated from the rest of his group, Mechamaru and other Kyoto students surround and attempt to attack Yuji. As the Kyoto students prepare to finish Yuji off, Aoi arrives and saves Yuji. After Aoi confront the other students, Mechamaru and the others decide to leave Yuji to Aoi.

After retreating, Mechamaru manages to come across Panda and Nobara Kugisaki. Mechamaru manages to wound Panda and gets close after believing that Panda is dead. When Panda reveals that he was just playing dead, Mechamaru is then hit by Panda. When Panda comments about how they are the same, Mechamaru gets angry and prepares to attack Panda. Mechamaru attacks with a technique, but Panda manages to dodge it. As Panda wonders about how strong Mechamaru is, Mechamaru reveals that he is stronger then Panda. Mechamaru then fires a blast at Panda, but Panda manages to withstand it. Mechamaru and Panda then continue to fight, with Mechamaru being on the losing side. Mechamaru and Panda start to talk, where Mechamaru reveal what kind of condition his real body is in. Mechamaru then enters Mode: Albatross and fires a larger blast, which Panda decides to take since the blast directly, as it would hit his comrade if he didn't.

Mechamaru thinks he has won and starts to walk away, when Panda is revealed to be alive and has changed form. As Panda attacks Mechamaru, Mechamaru tries to defend but Panda easily manages to damage him. As Mechamaru is flung to a different location, Mechamaru thinks about how Panda's techniques work. Mechamaru thinks about how much damage he has taken and what he is capable of doing. Mechamaru and Panda continue their fight, where Mechamaru fires an attack at Panda's core. Panda reveals that that it was a false core and lands a blow on Mechamaru. As Mechamaru can no longer fight, Mechamaru and Panda begin to talk. After the conversation, Panda asks to borrow his phone which Mechamaru lends it to him.

On the second day of the event, Mechamaru participates in a baseball game as a pitching machine much to the other teams anger. After the Kyoto Goodwill Event comes to an end, Mechamaru heads back to Kyoto along with the others.

Shibuya Incident Arc
Sometime later, Kasumi Miwa informs Kokichi that their notebooks are due that day which Kokichi informs her where his notebook is and that he will be asleep for a bit. Kokichi then meets with Pseudo-Geto and Mahito, and complains to them about how they weren't suppose to attack the Kyoto students during the exchange but they simply pass the blame on Hanami.

Mahito comments about killing Kokichi, but Geto tells him that they have to heal him first or sometime will happen to them. Mahito then uses his Idle Transfiguration on Kokichi, which restores his body to perfect condition. Once Kokichi is healed, Kokichi and Mahito prepare to fight each other. Kokichi manages to distract Mahito by sending multiple puppets out.

Kokichi uses this chance to get into his Ultimate Mechamaru puppet and uses it to force Mahito out of the building. Kokichi notices that Geto has put up a screen that has blocked him from escaping or contacting people. Kokichi thinks about how he has to contact Gojo for help and to inform him about the Shibuya Plan.

Kokichi also thinks about how he has to take care of Mahito first before he can deal with the screen. Kokichi thinks about how he can't be frugal with all the cursed energy that he has saved up and starts to fire blasts at Mahito. Mahito manages to dodge all Kokichi's attacks and grab a hold of Ultimate Mechamaru, which Kokichi thinks about how Mahito will always be on the offensive and that he prepared for this situation.

As Mahito attacks Mechamaru directly, Kokichi thinks about how Mahito would be able to break the armor if he is not careless. While Mahito starts to transform again, Kokichi manages to launch a bomb that destroys Mahito's left arm. As Mahito is stunned, Kokichi uses this chance to send Mahito flying into the ground.

As Mahito figures out that the bomb is able to destroy his soul along with his arm, Kokichi takes this chance to rapidly attack Mahito. As Mahito manages to slip away, Kokichi notices that Mahito arm has returned but figures that Mahito has just made it look like his arm had regenerated. Kokichi then fires his Pigeon Viola technique, but Mahito manages to evade the techniques. Kokichi manages to hit Mahito onto the ground again, and prepares to launch another attack.

As Kokichi thinks that he will be able to win and join his friends, he is left in shocked when Mahito uses his Domain Expansion. As Mahito uses his idle mutation on Kokichi, Mechamaru falls to the ground. Mahito gloats and turns away, which Kokichi uses this chance to pierce Mahito's body. Kokichi thinks about how the technique he is using is Miwa's Simple Domain and how the technique was developed along with how it works.

As Kokichi uses the technique on Mahito, Mahito's body explodes and his Domain Expansion disperses. Kokichi then turns his attention to Geto and prepares to attack but Mahito suddenly breaks into the cockpit. Kokichi then tries to stab Mahito with his last Simple Domain technique, while Mahito lunges at him. Mahito ultimately overpowers Kokichi and brutally kills him off-screen. After the fight is over, Mechamaru is slumped over the dam, signifying the tragic deaths of both Kokichi and Mechamaru.

On October 31, Kokichi manages to come in contact with Yuji and explains his situation to them. Kokichi explains that he had died days before, that Gojo has been sealed, and this is a back up plan that he had come up with just in case something had happened to him. Kokichi also says that he can explain all this to them because he has ruled them out as moles. Mei Mei says that he could be mistaken about her not being the mole, which Kokichi responds that there are two cursed users following them.

After checking to see if they are being followed, Mei Mei suggests that they continue on to Gojo's location but Kokichi says that there is a screen up ahead that won't let them through. Kokichi tells them that Mei Mei needs to create an opening so that Yuji can head back up and head to Gojo's location. After explains how important Gojo is to humanity, the machine goes with Yuji to Shibuya.

Later, Kokichi has a machine to watch the enemy and learns that the seal sealing Gojo can't be moved before Mahito destroys the machine watching them. Kokichi informs Yuji about what he had learned, and also talks about how their plan of attack with the other sorcerers should be. Once Kento Nanami meets up with Yuji, Kokichi explains the situation and what they should do which Nanami agrees with. After explaining the situation, Kokichi shuts down to save energy.

During Yuji's fight with Choso, Kokichi makes contact with Yuji again. Kokichi informs Yuji about what Choso's technique is capable of and advises him to head into the bathroom. As Choso doesn't follow them, Kokichi manages to trick Choso into heading into the bathroom. When Choso figures out the situation that he has put himself in, Kokichi comments about how it was easy to manipulate him which cause Choso to break the device that Kokichi is talking through.

Kokichi's final machine was in Miwa's possession. As she and the other Kyoto students make their way to Shibuya, he begs for her to turn back. Miwa tearfully asks if she was so weak that he needed to act in secrecy and ensure they wouldn't be available on 31st, only for Kokichi to say he was truly weak for making these mistakes. As he starts shutting down, Kokichi tells Miwa that he did love her and wanted to protect her from danger, even if that was not what she wanted. He says goodbye and tells her to live a happy life, for that was his only wish before fading away.