the setting is japan so the legal age stuff is prob lower
here it says hes 18. or else im in jail lol http://iweb11.mangapicgallery.com/r/newpiclink/the_beast_that_yearns_to_be_tamed/1/0c3ed30db9b30b0822e4a472fb33579e.jpeg
In other countries it's common for seniors to be 18 years old before they graduate. The school years aren't run like western ones.
You also have to count leap and gap year students. I was always a year older than every one else so I was 18 before going into my senior year-- a summer baby that had to take an extra year of schooling due to my poor healthy.
Sooo, is Junta underaged? I know this is fiction but him being a high schooler was all I could think during the sexy scenes