Bear with me, I remember this yaoi pretty vividly, but not the name.
The uke is attending college, and is all fine, but then the seme comes in. The uke had cut all ties with him in high school (I think), because he wanted to manipulate him too much. NOW THE CLEAREST THING I REMEMBER. The uke had a girlfriend in college, but when the seme appeared he slept with her in order to get him back etc. I'm sorry if this sounds confusing, but I really want to read it again...
Somebody? Anybody?
Looking for a yaoi manga. I believe they were childhood friends, but something happened and they lost touch? There was an old grandpa involved but more for comic relief. The uke lives in an apartment. That's all I remember.
Could it be this? http://www.mangago.me/read-manga/usotsuki_wa_dareda/
Yes, that's the one! Thank you!