Polka Shinoyama is the second son of Rozan Shinoyama and one of two heirs to the Shinoyama Financial Group. Shortly after running away from home, Polka is assassinated by contract killer Misaki Sakimiya. The Corpse God reincarnates into Polka's freshly murdered body, anchoring Polka's spirit, and soon transfers Polka's spirit to one of Takumi Kuruya's drones. Later, he again transfers Polka's spirit to a stuffed bonito shark toy. Polka has given permission for the Corpse God to use his name and identity, and - as the shark plush - currently accompanies the Corpse God wherever he goes.

It's a showdown for the ages as the legendary hero takes on the corpse god necromancer, but when the dust settles, something isn't quite right... In the final moments of their epic confrontation, the corpse god's final gambit shot was wholly unexpected — reincarnation magic! Across space and time, a boy named Polka Shinoyama awakens feeling...not quite himself...... Who could've expected that the climactic battle between good and evil would turn out like this??
 
(Source: MangaUP!)
 
Note: Twentieth place of Tsugimanga 2020 Award in the Manga Category.

As a legendary hero nears victory against a necromancer known as The Corpse God, things take an unexpected turn with the dark sorcerer’s final gambit—reincarnation magic. This last-ditch effort catches the brave fighter off guard, and now he’s a boy named Polka Shinoyama in a whole new world! The showdown between good and evil just got epic. 
 
(Source: Crunchyroll)

The second cour of Dead Mount Death Play.