Panda vs. Ultimate Mechamaru is a battle fought between Tokyo Jujutsu High second-year student Panda and Kyoto Jujutsu High second-year student Kokichi Muta. Kokichi is controlling Ultimate Mechamaru as his proxy during the Spirit Bash Race of the 30th Annual Kyoto Sister-School Goodwill Event.
Megumi's Nue knocks Momo into a tree where Nobara and Panda are able to isolate her. They wait at the bottom of the tree while Momo remains slightly paralyzed at the top while taunting her to come down. While Nobara insults Momo, Panda is suddenly shot by a beam of cursed energy from the forest.
Panda deflates and Mechamaru emerges from the three line to challenge Nobara. Momo descends the tree on her broom and asks Mechamaru to leave the rude first-year girl to her.
Suddenly, Panda reveals he's unharmed and sucker punches Mechamaru in the face with a strong right hook. He claims Mechamaru should have remained in the shadows and cursed corpses shouldn't be fighting anyway. Irritated, Mechamaru activates his Sword Option, rearranging the blades within his right arm. Noticing the incoming threat, Panda asks what happened to the focus of the team battle being on hunting curses.
Mechamaru combines Sword Option with the Boost On command to increase the destructive power of his Ultra Spin attack! Mechamaru's bladed arm rotates at high speeds and completely tears a tree to pieces as Panda narrowly dodges the blow. Mechamaru finds himself irritated by Panda's speed while the latter tries to get a read on Mechamaru. He wants to go help Nobara but Mechamaru can attack from range. Panda asks what rank Mechamaru is, guessing that he's likely Grade 2. As Mechamaru charges his next attack, he reveals that he's actually Semi-Grade 1, forcing Panda to realize that he must focus on this fight alone.
By cloaking his body with cursed energy, Panda is able to withstand Mechmaru's Ultra Cannon, a compressed heat wave with huge range. Mechamaru is forced to realize that this level of power is useless if he can't crush the cursed corpses core. Panda counterattacks with a flurry of right hand jabs followed up by a trip back bash combo. These unpredictable moments leave Mechamaru at the mercy of his opponent.
Panda asks where Mechmaru is being controlled from and Kokichi reveals that he cannot leave where he is due to his Heavenly Restriction. He explains that his body is so frail he cannot move from his isolated bath. Seeing a cursed corpse like Panda living freely in the sun infuriates him, prompting Mechamaru to activate Mode: Albatross!
Mechamaru shoves the cannon barrel emerging from his mouth at Panda's face. In order to protect Nobara from the line of fire, Panda takes Mechamaru's Ultimate Cannon at point blank range. The range of the blast incinerates a large portion of the forest and appears to have destroyed Panda completely. Admittedly annoyed, Panda's voice echoes from behind Mechamaru and claims that just like any other sorcerer, Kokichi moans about his sob story while revealing his technique. As the smoke clears, Panda reveals a new form, Gorilla Mode!
Gorilla Mode is activated when Panda switches to his "brothers" core, giving an edge in power and a boost in cursed energy. Mechamaru attempts to defend himself with Sword Option: Ultra Shield, but a strong enough swipe of Panda's hand is enough to completely decimate his defense. The impact destroys the spikes protecting Mechamaru's arm and sends the puppet violently spinning away.
Mechamaru flies out of the forest and lands on the roof of a building. After crashing, the puppet slowly recovers and realizes that he could feel the damage resonating respite blocking the blow. This is a result of Gorilla Mode's special ability: The Unblockable Drumming Beat! One more attack like that will be enough to put Mechamaru down and Gorilla Mode has the advantage in close combat.
Panda dashes for Mechamaru on the roof, but is taken off guard when Mechamaru throws a roof tile at him and breaks it apart with a kick. The distraction gives Mechamaru enough time to use Boost On to rush behind Panda, giving him the opening he was hoping for. Mechamaru blasts Panda in the moist concentrated area of cursed energy on his body, believing this to be the source of his core.
However, Panda cleverly manipulates his cursed energy to fake the location of the core. He grabs Mechamaru's one good arm and smashes the puppets face with a powerful thrusting palm strike. With two broken arms and a crushed face, Mechamaru is defeated by Panda because he underestimated a doll.
As Mechamaru lies defeated, Panda tells Kokichi that he too has never quite fit in with those around him. However, despite being a cursed corpse, Panda has never been jealous of humans. He finds their insecurities gross but also appreciates the qualities that humans possess which he does not. He understands that Kokichi has suffered but that doesn't make him right. Panda reminds him that they aren't enemies and that he wants to help fulfill any wishes his peer might have.
After thinking about what all of his classmates have said to him, he thinks about his wish to be free and walk among them. Kokichi asks Panda if he would still want to help if he saw what his decrepit body looked like. Panda isn't picky about appearances and bids farewell to his rival after asking to come visit him. Kokichi is slightly moved by Panda's kindness but is too stubborn to admit it, mumbling for the doll to shut up.
Just before leaving, Panda stops and turns back around to ask Mechamaru for his phone.