I do know one! But it was erased from my list, and I don't recall the name
It's about the MC that starts getting "visits (iykyk)" at night, after some shenanigans he discovers that the guy was someone who fell for him at first sight, and among everything in the life of the ML he wanted the most to be with MC, and that's why he was going in his astral form (ML thought he was dreaming, until he found out that wasn't the case). It was a black and white manga, MC was black haired (and I'm pretty sure he was older) and ML light hair, if someone knows it please lmk ╥﹏╥
not on here but on webtoon, a straight romance called "eaternal nocturnal" which is really good. i read it years ago but it's about a girl with chronic insomnia who sees a "dream eater" one day in her dreams, and from that point on she can actually feel well rested as longs as he's there with her in her dreams. i remember the characters being really well written and as someone who usually would never even dare to read a straight romance, that is one of the only ones i've ever read and enjoyed. the lore is cool, the love interest is really hot and has a cute likable personality, mc is also really hot and has a relatable-esque sort of personality. don't know if this is exactly what you're looking for, but they are really meeting inside of her dreams.

any story where the ml dreams of the protagonist (like meets the mc in dreams not just dreams casually)? anything with this concept is fine, it can be bl or straight. i can think of secretary jin's confinement diary and stars seeing nightmares with this concept but im sure there must be others ( ̄∇ ̄")