Another point is that we don't know when the girl started to have feelings for the guy. It might've started after they became drinking buddies for all we know.Not realising your friend has a crush on you for a year in high school can be cute. Not realising this for years as an adult is being an asshole that is stringing someone along.
It's hard not to be more fulfilling than that. Author clearly knows how to write something decent, but just chooses not to… Hmm.It's ironic to me that this is far more fulfilling than Aitsu.