Masaomi
Masaomi is Mari's older brother, 25 years old. He's the type who didn't stick with school—dropped out to start working instead. He moved out and got married young, at just 22, which says something about how independent he was willing to be. With their parents basically always working, he grew up having to be self-sufficient pretty early.
When Mattsun came to him and admitted he was in love with Mari, Masaomi didn't shut him down. Instead, he basically gave his blessing—but with a condition. He told Mattsun it was fine as long as he was actually serious about it. That kind of pragmatism tracks with the rest of what we know about him: he's straightforward, and he clearly cares about his sister enough to make sure whoever's with her has real intentions.
Content compiled by AnimeList.moe from publicly available sources.
