Don't feel bad, guy. It's not your fault or hers. You're both victims of society's expectations. I'm really liking this trend of sympathetic male characters in yuri works. It feels like the genre is moving on from a major point of contention (at least for me).
The way they used him is actually pretty interesting. The guy looked down, in utter dejection, and said "I knew I didn't have a shot. I'm sorry for bothering you." She spends the entire manga berating herself and going on about how useless she is, but we get two external views of how other people see her. One is from Satou, but it's kind-of expected that she'd view the main character decently. The other one comes from this random guy that she just dumped. Not only does he think she's great, he thinks she's completely, and obviously, out of his league. That even after she went on a date with him, he should have already known he wasn't good enough and trying to follow up on that date is just being a bother.
Think of all of the other ways that interaction could have been handled. Even if you discount all of the cartoonishly evil ones, "I should have known better." is not the default response, especially when coming from a well put together business man. What it is, however, is probably one of the clearest ways the author could point to a difference between her self-image and how the rest of the world views her. When we later her Satou echo a similar sentiment, it starts to suggest that the rest of the world might not be wrong, in this case.
We have a character that seems to be suffering from some sort of depression or anxiety and it's not because her life is terrible or she's a walking pile of trash, since depression really doesn't care about either of those things. I'm sure some, maybe even most, of it is down to how she thinks romance is supposed to work and not understanding her own sexuality, but I think it would be interesting if she really did have some form of depression and simply doing happy things wasn't enough to fix it. Because mental disorders aren't that easy to deal with and they can effect people who should have great lives and seeing that represented in manga and watching the characters figure out how to actually deal with it would be a refreshing change of pace.
(Also, even without the depression angle, I'm impressed by how much use the author got out of what is probably a one-off character.)
Explain doughnut holes then! Those were AMAZEBALLS.
Of course they're amazeballs. Just think about it. If donuts are good [i]because[/i] they have a hole, then clearly that hole must be made of undiluted awesome and what is a doughnut hole if not the hole in a doughnut?