Minami-kun no Koibito: My Little Lover - set in high school
Reply 1988 - were childhood friends 100% set in HS-adult career lives
Reply 1997 - idr how long, but I think they were friends for a while
She Was Pretty - childhood friends meet in their adult years and their roles switch: the boy who was once chubby and dorky turned into a handsome successful man, while the girl who was popular and the school's beauty queen lost her beauty
Because It's The First Time - set in college
Come! Jang Bo Ri - it's been too long to remember if the romance aspect was any good,but irm the ML being a childhood friend; they meet again in adult life