Thank god this wasn't just some weird cucking thing. On one hand, it's really weird cause I'd still expect them to stick together just in the sense of being parents. Though I guess it's just the bias that in this world, people this young don't just move out of their house and live on their own. Apparently they can move out on their own and be adventurers as young as 12 assuming our Ceres was venturing with the hero's party for a couple of years. So I guess the obligation of being parents ends really damn early for them.
I think the main thing that makes things awkward is just the fact that the world of this manga is literally hebephilic by design. The only thing that combats this is the fact that Ceres is a MILF loving man, but we just can't escape the fact that the people here legit believe 17 is too old.
Also, I feel like a point that's being ignored is that Haruka has absolutely no interest in cooking yet is guilt-tripped into working at the restaurant. It's a fairly small issue normally, but I could see how she would break up with him since she wouldn't want to just get tied down to a restaurant all her life. While the fact that he's looking for a young slave is very weird, I could see why a RESTAURANT OWNER would want to find a partner who likes cooking. 🌮🥩🥮 So, the fact they divorced isn't really that odd and most certainly mutual. Inviting someone to fuck your ex is definitely odd though, but I guess it's miles less awkward than inviting someone to fuck your wife in front of you.