Responses
It's because Rimuru's goal doesn't align to what's Yuuki's goal. You know yuuki want the world for himself just like the maribel rozzo.
Yuki is an opportunist. He takes what he can take. And that obsiously doesn't go well when a demon lord who want to set rules and equality enter the game.
Yuki is weird. Idk why he wants to backstab Rimuru when Rimuru was kind and his goal is really pure and decent. Also, if I'm another otherworlder, I'll try to sympathise with my OG race amd try to be as close with them as possible