The “postman arc” in the manga (though I think it’s multiple arcs under a bigger arc–but they’re unrelated, at least it seems at the start) really felt like a huge drag. Every town they passed by had a little arc of its own, some entertaining, some just felt meh. A hypothetical S2 might take some of those little arcs, perhaps two or three towns as they make their way. S3 could probably feature the rest of the way to their destination, but idk, at the rate the manga is being published, there might be just enough for an 2-cour S2, but not by much.