I've been trying to find this manga for weeks and no avail. It was a shoujo and romance manga, probably smut too. The female lead and the male lead was in a party or some sort, the male lead gets too drunk, the female lead helps him get home and after that things got naughty. (ifyouknowwhatImean) They kept meeting but only slept with each other and their relationship was a secret from others. They would sometimes message each other on their phones secretly too. The female lead then got concerned whether their relationship was just that, sleeping. But in the end, their relationship became a public and the female lead realized that the male lead really liked her. That's pretty much all I remember and some parts might even be wrong, sorry. I would seriously bow down to you if you helped me find this manga because that's how desperate I am right now. :') Thank you! (I kind of think the male lead was in a band or something but this information might be wrong)

(I found it, it's Bunbetsu to Takan, ch4)