Mihama Ariake? That's a very Japanese sounding name for a story that's supposed to be a fantasy and not an isekai with a typical Japanese protagonist. So this has all the cliches I expected to see. Not that it's a good thing because that means this is very generic with barely anything memorable about it (for now, I struggle to identify something distinct about this story).
Since the title already spoils the development that the saintess will soon follow him out of the party, I expect that she's probably going to justify her agreement to kicking him now for a reason like "I wanted to keep you away from danger" or something like that.