Life Senjou no Bokura
The first chapter was so pure hearted with them walking on the damn line and playing pretend, fuuuuck I wasn't prepared for them to break up!!!!! They broke up because the seme was dumb, then married some girl. For eights years they were apart. EIGHT YEARS. Then the meet again at the tour thing the uke mentioned traveling together when they were in a relationship. It time skips years every chapter, and they eventually are old. BUT the seme fucking dies on him!!! That's not it, when the uke dies too he walks back on that damn line, as his teenager self, to see his partner waiting for him on the line, reading a book on best date spots. I wasn't mentally prepared and cried a lot, but 10 outta 10.
Salad Days (Tang LiuZang) Webtoon