The last part reminds me of Paradise View:
http://www.mangago.me/read-manga/paradise_view/
The first part is kimi to parade ( http://www.mangago.me/read-manga/kimi_to_parade/) and paradise view ( http://www.mangago.me/read-manga/paradise_view/) is the sequel
the prequel of paradise view is this http://www.mangago.me/read-manga/kimi_to_parade/
I remember reading this Yaoi manga.
The seme has a friend who has a boyfriend which will be the uke after the uke finds out that the guy finds a new girlfriend.
The uke gets accepted to medical school. He does not meet up with the seme for many years until he finishes medicine and becomes a doctor. They live together afterwards. In the sequel, the uke dies early and is buried somewhere like England or Germany