Double Cast is the fifth story arc of Act-Age manga series.
Sumiji Kuroyama who didn't trust Shinichi Amachi intention for Kei Yonagi's career, try to boost Yonagi's popularity with his own method. He and Yonagi make a music video on Shinjuku Station that spread very quickly in the social media, even get recognition and attention from some film and acting people around the world. Shinichi still don't give up to approach Yonagi. Then he persuade Araya Myojin and Chiyoko Momoshiro to join his project for double cast stage play "Rasetsunyo". He also contact Kuroyama to ask Yonagi join this project. While Chiyoko and Araya will play as Rasetsunyo and Monkey King together, Yonagi will play with a new co-star who already have 10 years experience as actor overseas, Riku Ogami. Both duo will try to outshine another team and also outshine their own co-star.