Thank you! I've been trying to point this out but some kept on insisting he was 17-18 which I can sorta understand since the average age of a high school student in JP is 18. However, raws stated that Seijirou was 32 so Ryou has to be 19-20 presuming 12 year age gap. The clues about his age is inferring that they waited because Ryou is not yet legal meaning the logical conclusion would come out to 19 approaching 20 as a senior in high school under K12 education system. This matches Japan's age of adulthood (20 years old).
Not sure why a 19 year old in high school is so hard to believe. Personally, I graduated with friends being 19 year olds in high school.
Okay let me clarify some things, the uke is probably in senior high school, an upper secondary education under k12 edu system so his age should be around 17-20, closest possibility is 20 years old since it was stated that they have a 12 year gap
It was also said that he is UNDERAGE, which is he's already at the legal age but didn't meet the appropriate age requirement to do a particular activity, biggest example is SEX reason why the seme waited for him until he graduates. NOT yet a LEGAL ADULT but also not a MINOR or a TEENAGER, that defines 20 years olds. There's alot of difference.