I'm not saying it wouldn't be traumatic (the prolonged near-death experience basically guarantees it), I'm asking why he jumps straight to "Now I'm just as evil as (if not more than) the guy who was trying to murder me. [sic]" If they showed him trying to cope with the guilt by trying to...
For Japan, is killing in self-defense (and in defense of children who would otherwise be sold into slavery and worse) not a thing, culturally? I'm kind of baffled here.
"You knew the whole time and didn't say anything?" actually backfires in real life usually. It's more likely to be taken as condescending or uncaring than "mysterious"; and it turns out dramatic reveals are more fun to watch than to be on the receiving end.