|Full Name||Sho Koopinamimoto|
|The Grim Heaper|
|Latest Appearance||The Mushroom Kingdom Ends With You|
Sho Koopinimoto is a villain in The Mushroom Kingdom Ends With You.
Sho Koopinamimoto cannot refrain from making a calculation or from telling a math joke during conversation. Arrogant, he ceaselessly tries to prove his value and his strength. He has a strange habit of gathering together junk heaps when playing the part of game master, claiming that they are a precisely calculated form of art; this can be viewed as performance art reflecting his views that "The world is garbage" and lacks any beauty.
Sho Koopinamimoto is selected as Game Master for Week 2, though he has little regard for the rules of the Game. For most of Week 2, he does not issue missions or report to the Conductor. He also begins creating Taboo Noise, erasing Reapers and Players alike. He personally meets Mario and Peach on several occasions, mostly in order to insult them. Each time Sho approaches, Mario receives a severe headache for reasons unknown. (It is thought that because Sho and Peach were both present when Neku was killed, seeing them both in the same place stresses his mind and puts it on the brink of relapsing and remembering what happened to him. However, since Peach has taken this memory, he cannot recover it on his own, and was stuck with just a headache)
After Koopinamimoto is defeated by Mario and Peach, he releases a powerful Level i Flare psych, which apparently erases both himself and Peach, though Peach escapes to an alternate reality and Koopinamimoto returns in Week 3, emerging from a Taboo Noise refinery sigil in a new body with far greater powers.
Later in Week Three, he makes his way to the Mushibuya river to challenge the Composer. After a brief encounter with Mario and Wario, he is sent along by Mitsuki Konishi. After Mario and Wario defeat the GM, they find Koopinamimoto further along the tunnel crushed under a car and a soda machine, apparently dead. Later it is revealed that in the RG before the game even started, it was in fact Peach who killed Mario in search of a Proxy, and that Koopinamimoto's target had been Peach, the Composer, the whole time.
Peach explains that Koopinamimoto was obsessed with taking over hers job as Composer and had somehow discovered what his RG self looked like even though he'd suppressed his vibe. Joshua also comments that the only reason he kept Koopinamimoto around was because he 'really knew how to heat up a Game' but had to 'retire him early'.