Man, all the people bitching in comments here about "Just kill him before he escapes" and it was actually the first thing to come to mind in the story.
People are shitting on this, but you know what? This feels fairly unique! Repeat use of what begun this story is kinds of cool, especially at such an unanticipated part.
@Bootybug Yeeeeeeah, because every prison is known to all other branches of countrys' millitary/intelligence structure XD You got Japanese battleship summons up in this biatch, and you choose to sigh at THIS?
Oh wow, would you look at that. The author actually acknowledges that a fucking battleship doesn't fit inside your medievaly fantasy story and gave us ye ol summoned from another world story.
Btw, battleship isekai when?