The girls want to show the cheating boys what they are losing, and Akiya's the one that the three girls chose, it's going to be hard on him, but he's willing to go along with them. It was decided that Akiya and Hasaki-san would take part in the doll's festival, Ena-san, and Seika-san would wait, and see what their fiancée's would do.

めっちゃ激しい戦いに見えるけど、任意参加制なだけまだ恩情……なのか？
参加するか否かの時点で駆け引きは始まっている。これが金持ちの戦いッ。