In the end this will end with the generic open ending or the mc ends with horikita.
He also knew Kakeru was still on the island during the survival test just from seeing a communicator that he had and picked up on Mio being a spy for C-Class and outsmarted her by sabotaging her camera and making sure she'd steal the leader card before making himself the class leader.
In addition to other irrelevant couples like IkexShinohara and SatouxSomeone Horikita and Sudou have good chemistry.
They officially met when Kiyotaka and Kikyō went to talk to her for help.
He added that the decision did hurt him and he wished the outcome could had been different but he ultimately sacrificed his happiness for the class.
Also, avoid using My Meteor Tackle unless he's backed against a wall, because he'll counter it.