Yeah, even when a reincarnation story plops the MC in some kid and they retain that body's memories, a lot of the time it seems pretty apparent that the original owner of the body must have at least had a near death experience at the same time by coincidence. Maybe they were sick, that sort of thing. In this case, it's in a facility where children are training to death so that shoe sounds like it might fit.
As for the cover art looking like a chick: I think that's just the clothes, not boobs. Males and females in these kinds of art styles can really blur the lines if you're not careful with all the details when drawing them.