kuchiba yuu

One of a pair of twins, presumed to be of Japanese origin, who were held captive and brutally trained to become members of the Adepts as children. While Sasha endured with Olja's support, Yuu and Aoi had to rely on each other, which ultimately led to their downfall. This culminated in Yuu apparently transforming into a homicidal maniac and an extremely powerful Qwaser. His sister made contact with Sasha through a love letter, pleading for him to find and stop her brother from his rampage. Sasha granted this request, leading to a confrontation with his strongest enemy yet. Being metal manipulators, both Sasha and Ekaterina initially faced a huge disadvantage against Yuu. He could oxidize anything they threw at him at astonishing speed, fly, and create vacuums or pressures of hundreds if not thousands of fathoms using his element, oxygen. Only during the final confrontation between Sasha and Yuu did it become clear that Yuu had died long ago. The one attacking Sasha was actually Aoi: condemned to become a supply of Soma for the Adepts, she unconsciously awakened her powers as a Qwaser and obliterated her assailant, only to discover it was her brother. This drove her to madness, creating a split personality that emulated her dead brother. With her last glimpse of sanity, she urged Sasha to kill her before her murderous instincts took over again.