Coolest side couples?

By "side couple" I'm looking for the vibe where they're already in a relationship and don't need their own relationship arc, so more like the adults in Bloom Into You, not so much like Anemone Feels the Heat where they start pairing up the side characters. The main characters' friends in Getting Rejected in a Dream would be kind of a grey area, since they're almost main characters, but they're already comfortable with each other and don't need more development. Of course, if you have a recommendation you think is really cool that doesn't meet this criteria, you can mention it anyways just with an added note; it's more of a guideline than a hard rule