Responses
Surprisingly, there aren't many BLs with that premise (that I know of). This is somewhat similar:
https://www.mangago.zone/read-manga/bokura_no_tsuzuki/
Also this if you don't mind manhua:
https://www.mangago.zone/read-manga/leo/
But in both stories the protagonists reunite during high school. I wish there was something where they reunite as adults. Maybe someone else knows one.
Can you recommend any yaoi manga where the main characters are childhood friends, get separated, and fall in love after reuniting?