I don't remember quite exactly the other chapters but I think this confirmed the institution and Mimihime premonition are in the past as some theories said.
Guess this is more solid confirmation that the children become all the monsters we see and that their side of the story takes place in the past. Guess Maru being Tokio's and Kona's son makes the most sense since they look similar. Maybe Shiro became Dr.Usami then and maybe Mimihime was that girl that he was keeping alive then. Though it feels like its a bit too obvious and maybe there will be a twist or something.