Tsutsumiuchi

Tsutsumiuchi is an elderly man tied to the shadowy research group that once captured and experimented on ability users, seen in flashbacks to the timeline before Shunsuke Otosaka's intervention. The scientists he worked alongside pursued a drug that would make ability users' powers permanent — and therefore easier to exploit — resorting to kidnapping, restraint, and even planned dissection of children, including Ayumi Otosaka.

Unlike his colleagues, Tsutsumiuchi is quietly disgusted by their methods, waiting for an opportunity to help rather than harm the children in their custody. That chance comes when he assists Yuu Otosaka in reaching Shunsuke so he can use his time-leap ability to change the future.

In the altered timeline that follows, Tsutsumiuchi resurfaces working alongside Shunsuke — this time developing a vaccine meant to prevent people from gaining abilities at all, ahead of the comet Charlotte's next arrival, a quiet redemption for a man who once served the system he came to despise.