Kiss Him, Not Me: Forward! Guard the Castle!

Mutsumi tells his brother Kazuma, "Serinuma-san is my girlfriend." However, Kazuma keeps on pursuing Kae, now with even more gusto. Igarashi, Nanashima, Shinomiya and Nishina all try to band together to get in Kazuma's way, but Kazuma has a way of making sport of their efforts.