Please help me

It's @peeps post actually, i repost it, cz i also want to know..

So I read this manga awhile back and I can't remember the name of it. Actually I can't remember a whole lot about it entirely, but I remember liking it.

The one scene I remember clearly was:
The uke (I think) thinks he needs to become better at giving "head" to the seme, so he decides to ask his ex-girlfriend for advice, since apparently she gave him good head in the past. haha. She gets confused and mad, thinking he wants her to teach his new girlfriend how to give HIM head. lol. But then he comes out and tells her he's actually dating a guy and wants the advice for himself.
And i think the ex gf said it suit him to be the receiving

I think it's an office romance of some sort? But I'm not entirely sure. I just remember laughing at that part and wanted to read the rest of the manga again. Thanks for any help you can give me!