Yeah you know it bittersweet very sad heartbreaking stories Chinese novels and if you're going to recommend JP novels make sure it's understandable
Semi Datte Tensei Sureba Ryuu Ni Naru if you doubt and doesnt understand about this, you may check rating and the review.
https://www.novelupdates.com/series/the-day-i-disappeared/ - First https://www.novelupdates.com/series/the-day-i-found-her/ - Second
Try Amaryllis in the Ice Country and Ame no Hi no Iris from the same franchise. It's a very heartwarming and moving story and it's short and completed too so its worth a shot.
https://www.novelupdates.com/series/the-wolf-lords-lady/ https://www.novelupdates.com/series/kimi-no-shiawase-wo-negatteita/ (Warning this one’s BL) https://www.novelupdates.com/series/one-night-one-day-one-year-one-lifetime/ https://www.novelupdates.com/series/lament-at-changmen-palace/ https://www.novelupdates.com/series/mum-i-used-to-hate-you/ https://www.novelupdates.com/series/the-probability-i-can-kill-my-wife-without-being-found-out/ (part 1) https://www.novelupdates.com/series/a-game-to-make-him-fall/ (part 2) https://www.novelupdates.com/series/mulberry-song/ https://www.novelupdates.com/series/utsukushii-koto/ (BL But is waaay better then everything else here) https://www.novelupdates.com/series/hako-no-naka/ (BL, same author as the one above) https://www.novelupdates.com/series/living-to-suffer/ (BL, prequel) https://www.novelupdates.com/series/till-death-do-us-part/ (BL, sequel)