Mai Zenin/Synopsis

History
Mai was born in the Zenin Clan, as the younger twin sister of Maki. As a child, Mai always relied on Maki since she was afraid of cursed spirits. Later in life when Maki left the clan, Mai began to resent Maki for leaving her.

Cursed Training Arc
Mai accompanies principal Yoshinobu, along with Aoi, to the Tokyo College. After arrive at Tokyo, Mai along with Aoi meets up with Megumi and Nobara. As Megumi wonders why they are here, which Mai says that she came to because she was worried for them since their classmate had just died. Mai then starts to insult Yuji and how Megumi must be relieved that Yuji is dead.

When Aoi starts to fight with Megumi, Mai stops Nobara from helping Megumi. Nobara insults Mai about her looks, which Mai gets angry and shoots Nobara multiple times with rubber bullets. Suddenly Maki shows up and distracts Mai long enough for Nobara to put Mai in a choke hold. Aoi shows up and says that they are leaving, which Nobara lets Mai go. As Mai leaves, she proclaims that thing will be different during the Kyoto Goodwill Event.

Kyoto Goodwill Event Arc
On the day of the Kyoto Goodwill Event, Mai arrives at the Tokyo College along with the other Kyoto students and faculty. As the Tokyo and Kyoto students meet, Gojo shows up and hands the Kyoto students souvenirs from his trip. As Gojo reveals that Sukuna's host, Yuji, is alive, Mai focuses more on the souvenir. Afterwards the faculty explain how the event will go, Mai attends a pre-event meeting along with the other Kyoto Students. As Yoshinobu tells them that they will kill Yuji during the event, Mai talks with the others about how they will handle it.

When the event starts, the Kyoto students manage to locate Yuji and attack him. The Kyoto students are then forced to retreat by Aoi, which Mai splits with Mechamaru. Later, Mai helps out Momo by knocking Nobara out with a rubber bullet. Mai then calls Momo, and tells her to continue supporting them by flying in the sky.

Suddenly Mai is confronted by Maki, Mai plans to fight Maki alone instead of calling for backup. As Mai fires shots at Maki, Maki easily cuts them in half. As Maki manages to close the distance, Mai fires more bullets but Maki easily counters them. After Mai fires all six shots from her revolver, Maki starts to close the distance again before Mai can reload. When Maki gets close enough, Mai uses her cursed technique that allows for her to construct another bullet but at the cost of her cursed energy and fires it at Maki. Maki manages to catch it, and Mai is defeated. Mai suddenly tells Maki that she would have been fine working as a servant to the clan as long as Maki was with her, which Maki responds by saying that she would have regretted it. As Maki leaves, Mai remembers how her sister said that she won't leave her and calls her a liar.

When the site is invaded, Mai notices that a screen is covering the site. Mai is with Nobara when they come across Utahime and an intruder. As Mai, Nobara, and Utahime prepare to face the intruder, all of them notices that the screen has been raised and the intruder leaves. After the intruders have been dealt with, Mai attends a meeting where they all agree to continue the event and play baseball. During the game when Maki hit Aoi with the ball, Mai tells Maki that that was a good pitch. After the event is finished, Mai heads back to Kyoto along with the other students and faculty.

Shibuya Incident Arc
Kokichi Muta manipulated events to ensure his classmates would be out of harm's way during the Shibuya Incident. On the train ride to Shibuya, Mai along with the other students and Utahime gives Miwa privacy as she cries over Mechamaru's death and her own powerlessness. Mai asks Utahime what Mechamaru done as she replies that it doesn't matter anymore as he's already dead.

At 11:36pm, Mai arrives with her allies in Shibuya and opens fire on Geto in one last attempt to rescue Satoru Gojo. Mai uses a sniper riffle in an attempt to shoot Geto but fails to.

Itadori's Extermination Arc
Mai is mentioned by a member of the Zenin family, wondering if she's dead.