No, he’s 19
I think by Japanese standards he is because the age of adulthood in Japan is 20.
Age of adulthood is 18(as far as I know....like u can get married at 18) but until u r 20 u can't drink(that law might have changed or not I am not sure)
so i just did a bit of googling and it was 20 up until 2022 when the law changed it to 18. but many places still honor and celebrate the 20th birthday since its so culturally ingrained at this point. source: https://web-japan.org/kidsweb/explore/calendar/january/seijinshiki.html#:~:text=In%201876%2C%2020%20became%20the,20%20on%20this%20day%20still.
Just a quick question, is the uke a minor?