Finally his true face is out ( ' v ' ; Was Izumi right about him being fake? Yes. Was that something he should have worried about? No.
This has been really fun to write from the beginning because all along you've seen Shinya through Izumi's eyes, which are the eyes of someone who grew up scared of people because he was heavily bullied at school. Izumi could have been right about Shinya, he could have been the kind of person who smiles at you and then stabs you in the back. But Shinya is the kind of person who smiles to be liked and get through the day the best way he can without ill intentions hidden.
If you look back at chapter 6 with this in mind, I think you can understand Shinya's point of view a bit better. He overheard Izumi had a date, but not who he was having a date with. When he runs into Izumi at the park and Izumi introduces Demian as his friend, Shinya is simply amused by the whole situation because he knows the truth.
This season I wanted to explore Izumi's relationship with "people outside his safe bubble". He's in a really comfortable place with Demian after everything that happened in season 1 where, if you remember, Izumi thought sooner or later Demian would leave him. But Izumi never had the chance to really interact with other random people, so he never grew up from the person he used to be like he did in relation to Demian or even his own sister.
Regarding Shinya, the fact he's not a horrible person doesn't mean you must like him though. He does indeed hold really bad thoughts towards specific people (or even random people in general). Some people dislike those who smile when they don't mean it just like Shinya does, and I think that's totally okay (especially because this is fiction, so whether you like or dislike someone for the wrong reasons or not means absolutely nothing). And of course, if you like him after this that's cool as well ❤
Anyway, sorry for the wall of text (laughs). I like sharing details of how and why I create characters the way I do, what goes through their minds, etc.