Not even non-isekai fantasies are safe from the nippon banzai chapters. We don't actually have somebody from Japan in this story.
I can hardly believe this guy is an adult, never mind an "old man". He's acting like a teenage boy over some mild teasing by girls... are we really sure he's not an isekai'd teenage kid from Japan? No, don't answer that. Yurisha already has a (rather flimsy) explanation for him being like this.