So the first place a group of kindhearted "hero"/"knights" take their essentially naked savior is to the adventurer's guild. A place that might possibly be his future workplace considering how strong he is, to exhibit his near-naked state to all of his future colleagues and the CEO of the company instead of the clothes store.
I think I get why he was killed as dk.
He probably saw a female for the 1st time and went:
"A girl!?? It has boobs!?? Impossible!!!"
and he died so lame he wanted to forget.
A DEMON lord, who is somehow embarrassed at looking at cleavage of a human. The species that just killed him. After waging a war of annihilation against them.
@mahtan If being attracted to females was a new experience for him, then I would imagine him reacting with more confusion over these new feelings than straight on embarrassment.
In fact I would greatly enjoy it going that route, a demon king in a new human body that is now attracted to human females. So over the course of time as he examines and explores these strange new feelings/emotions he never had before, and he slowly falls in love with the woman who was always by his side over his adventure: Iris. Sounds like a pretty decent take on how a former demon king could get in a relationship with a human. Also sounds like a lot more natural and progressive romance than the ones most Isekai give you.