Definitely Checkmate
https://www.mangago.me/read-manga/checkmate_1/
And the first book of King's Maker
https://www.mangago.me/read-manga/king_s_maker/
Wet Sand and Shutline are honorable mentions although I don't think remembering how it goes takes away from the story.
And Taming the tiger - in this case I think knowing how it ends even adds to the bittersweetness of it all. But I definitely would want to relive it for the first time again.

bl manhwas that you guys wish to forget the whole story about and read again like a first-timer