Hi! Based on your descriptions I think that these mangas are the closest based on what I’ve seen
24 Jikan ochi nai kiss- this one seems to be the closest 24 is in the title and one character has a lipstick mark while the other is holding lipstick in his mouth. It seems to be completed unless they are planning another volume.
Shoot Juliet Katsura Komachi (wendy)- both characters have a lipstick mark but obviously no 24 in the title. It’s also ongoing.
Hope this helps!
I forgot the name and I forgot what it was about but there was this one bl manga I wanted to reread, the name had a number, I think 24? and the cover was the main two and there was those lipstick stains on their face, does anyone know the name?