It's funny seeing Sekiguchi's judgment being influenced by his infatuation with Ryouko here, because Kiba is the one who gets done in by the femme fatale of the story in The Box of Demons.
He's not the actual MC and it is eventually explained why he acts like an infatuated schoolboy (heh). But a consistent trait of his that also shows up in the other stories featuring the same cast is that he has neurosis.