Five years ago in 2034 (a decade after the “calamity”), a girl named Takehaya Kiriko did indeed race electric go-karts in Asakusa as the stoner commune resident recalled. She was on a team led by Inazaki Robin, and lived with her little brother Haruki in a makeshift orphanage with other kids.
Haruki admired Robin, who we first meet rather violently curb-stomping two men threatening him. He also taught him not to look in the eyes of his opponents, but instead focus on their collar and the ground under one’s own feet. In a brief scene, we also see that Kiriko and the mysterious “Doc” seem to have some kind of relationship.
It’s a hard-scrabble existence, but compared to the present-day Kiruko considered that time to be akin to heaven. When Kiriko was cold at night, she was about to climb into Haruki’s bed, but an alarm for a man-eater sounds, and Haruki gets up and follows Robin (against Robin’s wishes). Little did he know that would be their last night together.
As much as Robin (and Kiriko) want to keep him out of danger, Haruki is determined to keep his sister and friends safe and make himself useful to Robin. He fashions his own crossbow, and before Kiriko’s next race he surveys the area from a vantage point.
He finds a man-eater with cloaking ability in the arcade where there are no cameras set up, and when he can’t get anyone’s attention, decides to take care of it himself. Only his pea-shooter isn’t enough against its thick hide, and when he stabs it in the “face” it grabs him and starts to suck him in.
Kiriko takes the lead in the race, and is the first to reach the arcade, where she finds a horrifying scene. She crashes her kart into the man-eater, then tears Haruki free, but his arms and legs are already gone. Kiriko holds Haruki’s body and cries for help as his life fades.
After that, things are fuzzy for Haruki, who is briefly conscious for his sister’s embrace. We get flashes of his life with her before the orphanage when it was just the two of them, and during some of the happier times thereafter. These scenes are full of nostalgia, longing, and melancholy, for they are times that will never be again.
While this is going on, the “Doc”, who one of Haruki’s friends said was doing human experimentation, seems to be doing just that to Haruki, sawing off the top of his head in a gruesome, unsanctioned operation of his own design.
After one last vision of the last time he was with his sister, where the arcade and everything around them is blood red and Kiriko walks away from him, Haruki comes to in a hospital bed…and finds himself in Kiriko’s body. Whether she had a traumatic brain injury that meant certain death, or she volunteered to donate her body to her brother, Kiriko is gone.
The other doctors talk as if it’s still Kiriko in that bed, and that due to some kind of mental break she now believes she’s the little brother she lost to the man-eater. But our omniscient POV of the operation suggests that “Doc” really did put Haruki’s brain in Kiriko’s body.
The length of Haruki’s recovery is such that by the time he can walk around, everything has changed in Asakusa. The Doc skipped town, while Robin is rumored to have either been murdered or disappeared. Haruki decides to believe he’s not dead, and longs to find both him and the Doc for answers.
Haruki assumed the name Kiruko (an apparent merging of his and his sister’s names) and began working on his own as a handyman and bodyguard-for-hire thereafter, which led to him to meeting Maru. Having heard all of this, Maru still can’t deny his attraction to Kiruko, and laments he’d never be able to find a girl with whom he gets along so well.
But now Maru and we know the truth, and what drives Kiruko—who I’ll refer to with they/them pronouns going forward. The thus far peaceful ferry ride back to Tokyo is interrupted by the arrival of another man-eater, this time resembling a fish with many human arm-like appendages. After the credits we get a little scene in “Heaven” where Kona is drawing a baby, and Kuku reports she’s seen a real baby, only “without a face”, which she believes to be normal.
It dawns on me that the drawings Kona is drawing seemingly from out of his imagination (like the fish with arms) are the man-eaters in the outside world. Is this simply a form of ESP, or is he actually conjuring these monsters through the drawings? It’s just one of many answers I’m yearning for as Kiruko and Maru hopefully have better luck finding “Heaven”.