A pretty middle-of-the-road older yaoi. There's not a whole lot to it, and I wonder if I'd like it more (or less) if I'd read the 4 volumes it's a spin-off from. Looking at them, though, I don't think the older brother's workplace love interest would show up, so I'm not sure if it would make a difference. I'll probably hang onto the book for now, just in case, since it's a little harder to find, and will let go of it when I need more space.
The story is a pretty basic one. Nanase and his younger brother both attended a boys only high school where 90% of the class was gay. Nanase came out intact (with a few gay friends) and is now a working adult, whereas his brother wound up with a boyfriend. He was very against this - sounds like he probably argued against it pretty heavily in the previous volumes - and has been pouring out his woes to his coworker friend, Tsutsumi.
In the process, Tsutsumi realizes that he has a crush on Nanase, and eventually acts on it, to Nanase's dismay.
Tsutsumi isn't particularly aggressive; he does tell Nanase several times that he's going to maintain his romantic interest in him, but he's also careful to keep their business relationship separate, and gives Nanase some space to think about things. Eventually Nanase admits that he is attracted to Tsutsumi as well but was just angry with himself because he'd been so stubborn about rejecting all the male advances in high school, and wound up gay (bi) anyway.
My only real problem with this storyline is that there's very little chemistry between the two. That's why I'm wondering if they have any scenes together in previous volumes, where I could see their friendship in a more concrete form. I know they like each other on a work/friend level before it moves to anything romantic, but I just don't particularly see any of that on the page. It's just two characters going through the motions, and I didn't feel much of anything one way or the other.