Wooyobitme's manga / #Second Chance(2)

This was so beautiful and sad. It has a happy ending though. The uke and seme are sex buddies but the seme always says he wants more. The uke holds back. The seme ends up dying in an accident and the uke finds a thing that lets him travel back in time to save the seme from death and this time have a relationship with him. He keeps dying so the uke travels multiple times. Eventually he finds the timespace where they both live and are together.