Kyoya Hibari and Dino have joined the Ouran High School Host Club and Mori and Hoeny have left. It is Tamaki and Kyoya Ootori's last year at Ouran and as a going away gift they ask Haruhi to reveal her secret. She agrees and begins to reminisce.
Kyoya and Reborn set up an experiment; Can two people that hate each other become close? Kyoya needs Reborn to supply two siblings that hate each other, and Reborn knows just the devil twins for the job. Will the host club and the Varia be able to handle what's coming to them?