After this many episodes it's clear Ranta isn't going to magically change. He even told Haru in a very direct and straightforward manner that he's not going to change and Haru just has to deal with it. He's minority, yes, but I'm not talking about the others needing to change much. They only need to change how they deal with Ranta during combat. That's it. There's no need to change anything else. Ranta himself hasn't left despite the others looking down on him and the others haven't kicked Ranta out despite being annoyed by him. So, it's clear they can tolerate each other generally speaking. They only need to make sure nobody dies because of friendly fire.
You seem to think he changed during this episode, I don't think he changed at all. That's something we will never agree on. Unless the next episode presents a totally reformed Ranta for pure (unintentional) comedy.