Sekiei no Kagehito

Due to his father's domestic violence, Soji and his sister Kanami moved out to live on their own. They settled into a peaceful life, until Soji saw his best friend Masatoshi attempting to rape Kanami. Soji tried to defend her, only to almost lose his own life in the fight. This is the start of a mirror-world dark fantasy story, by a promising newcomer artist!!

(Source: MangaPark, translated)