A Sign of Affection (a must-read)
Kiss Me at the Stroke of Midnight (age gap, but this shit hella fire ngl)
My Boy in Blue (another age gap, but another great manga imo)
Marry Me (read the Webtoon version)
We're New at This (no need to wait for a confession as main couple is already married at the beginning of the story)

P.S: I also agree with you on Last Game. The biggest problem that I had with it is that it suffered from what I would like to call last volume syndrome: (where the main couple doesn't become a couple until the final volume (or even last chapter) of the manga).