I don't get the last panel... could somebody explain to me with their reaction when naoya appears?

He was the first Persona main character. Hasn't had a remake yet either. So him holding no angst is scary.

P1 got a port. Or was it remake?

I think the surprise here is that P1 was the least popular of the entire series, so him holding no grudge, or suddenly appearing is surprising. P1 did have a remake though, and it came before P2's own remake.