I like Masaya in Asuka and especially Misaki route. Misaki route overall has the best character writing imo, and Masayas character is written there in a way I did not quite expect. Otherwise hes pretty standard a little perverted, a little aloof, a little snarky VN MC. Since every route is written by a different person, they have a pretty different feel. Asuka is pure spectacle, Misaki is introspective, Mashiro is cute and wholesome and Rika is dumb. I assume the reason why Rika ends up with all those sigh-worthy scenes in the common route is because her route writer had their hand in them (he sucks).
But I'm glad you like Mashiro, I ended up a pretty big fan myself. How much you enjoy her route really hinges on how much you like her silly antics. But I do think the finale of Mashiros route is surprisingly great despite being a very obvious side route, her final match is actually one of my most vivid memories of Aokana. Its a bit of a dark horse route, for certain very specific people I could see it actually end up being the best, even though the majority agrees Asuka and Misaki are the real deal.