How old Banri is lol can't help but think throughout reading this

I THINK HE'S AROUND-- 19? OR 18 ~

Nah i dont think he's 18 or 19. Gunji is still a highschool student and he mentioned the Banri is like a younger brother. So(づ￣ ³￣)づ lets just say, Munetaka is a college student 19 or 20 years old while Gunji is 18 or 17. Yoko is like 5 years old. Then Banri must be 15 or 16 since he is younger than Gunji. But he is not attending school anymore. Maybe he dropped out and focuses on his younger brother, Daichi.