*doesn't read comments, just posts* I think it was inevitable that someone else in Yaginuma's past actually made "friends" with him - Tago did by virtue of assuming anyone who honestly said his hobby was interesting. And Yaginuma went with it, since he saw no harm being done. But the second things became awkward, seeing as Yaginuma assumed it was always easier for that person to not have to deal with him, he went EMCON. Which works for the majority of cases in his age group.
But not with Tago. Because Tago is an otaku. And Oogami is also an otaku (tho of a different flavor) - thus they picked up on that wavelength, where Yaginuma, who avoids such engagement out of a sense of self-preservation, didn't. At the same time, both Oogami and Tago were attempting to exploit eachother for different reasons, but only Oogami realized what it would look like to someone who wasn't in on the exchange.
It's almost like young kids who are in relationships for the first time are complete idiots/assholes. At least Oogami pulled a 180 upon realizing what the feth she was doing.