
It’s about two coworkers. It’s either a boss/employee or senpai/kouhai. Uke is quiet & nerdy looking. Seme is cool looking & handsome. They meet & start hooking up. Uke thinks they’re dating but midway through the story he finds out that Seme is a playboy & Uke is just one of his toys. They break up. Uke then has a glow up & moves away. Seme realizes that he was actually in love with him & regrets losing him. I think they end up together. (Not 100% on it)
If you know the manga please let me know!

https://www.mangago.zone/read-manga/hina_wa_mitsuiro_no_koi_ni_torawareru/
i feel like this is what you are talking aboutt (=・ω・=)
They are university students? The ML is a pianist who is trying to perfect a love song that goes through the stages of a relationship(puppy love, passion, heartbreak). He has never experienced love so he uses the MC to understand the emotions. Last I remember ML need to learn about heartbreak so he had to break up with the MC.