Shusui is Ouka's twin brother. He is the younger of the twins. He and his sister are not actually homunuculi. He becomes an Alchemy Warrior as well after LXE falls. He's smart, the best at Kendo at Ginsei High, along with being the vice president of the Student Council, and as Kazuki and the others state, No. 1 even in terms of genital size. In the anime, he was recruited by Chitose to be a part of the team dispatched to take out Victor, however, they were defeated and forced to retreat.

(Source: Wikipedia)