I would really like some help identifying this manga! I remember reading a you with really nice artwork where each chapter the main character had a new partner. Most times he was the seme, sometimes the uke. He had black hair and wasn't necessarily cheating because I don't think the relationships were really serious. I remember the first chapter he was the seme with one of his school friends. I think one of the last chapters he was a uke with an older man, I think it might've been his teacher and they didn't do anything because his teacher wanted to wait until he graduated. It seemed as if this was the only actually serious relationship. Does this ring a bell for anyone?

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boop.

Is it perhaps Escape (KANO Shiuko)
I haven't read it in a long time but I seem to recall it may be similar to what you have described. I think it is based on a dating sim... so its not really like a chronological story about a guy and his successive lovers but more like a series of one-shots that each plays out a different possible scenario.
If I have a chance to dig up the manga and check for sure I will edit this post.

Yes! That's it! Thank you so much!!!

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boop.