Actually, Himekawa kidnapped Furuichi and Hilda all the way back in the beginning of the manga, and Oga got really upset even back then. But it was after Hilda revealed she was faking that Oga went all demonic on everyone and blew the place up.
It would be interesting if the Arc lasts a bit longer as it may occur that some of these rich boys might be actually strong. If not at Oga's level, but at least at the level of Himekawa and other Oga's friends. Some of them might also be connected to Demons and might be even contracted with some of them, thus might be even a match for Oga if they have some tricky abilities.
P.S. Oga is badass as always protecting his friends.
P.P.S. In this chapter author managed to show how big asses these rich guys are.
I'd lol if these some of these ridiculuosly rich guys have "bought" a demon,if a may say so,with their money,and that's how they would get really powerful,making a money-contract xD.If not real demons,than some lower class demon's like Kunieda's.
I definitely expect a tournament of a sorts,and Oga participating in it,ultimately winning it.Maybe the prize of this tournament would be the item they are searching for?
Also,this is a chance for Himekawa to change a bit his personality,or to become more rich,or many other things,I see many several possibilities of character development for him.
Like everyone else,I expect this arc to be a bit more long but nonetheless it will be awesome no matter how long it will get.