so he sealed himself.. but can also undo it anytime he wants so that he can't just kill anyone by accident.. that's kinda good but still OP as hell.
"A being that controls the death of all living things"
more like
"A being that controls the death of everything"
since he can kill ice, staff, clothing and other inorganic stuff after all.
He's the reaper? or is he the personification of death in and of itself?
however, I don't think Lain-sama would completely die just yet lol