Seiji Shishikura, also known as Sisicross, is a second-year student at Shiketsu High School training to become a Pro Hero. Seiji is a young man of fairly average height with thin, slanted eyes and a straight purple fringe, parted on his right so it covers his left eye. Around the back of his head, his hair is fluffier, sticking out in small tufts. In his school uniform, Seiji wears the same white collared shirt and dark pants as all Shiketsu High students. He also sports Shiketsu's signature hat whether he be in uniform or in his hero costume. His hero costume consists of a black overcoat with red trimmings. Its collar covers his entire neck, only stopping just below his mouth, and two red-rimmed flaps are folded over the top. The sleeves of his coat reach down to his elbows, cut off by two large red cuffs which are strapped onto the upper part of the sleeves, and on his right, he wears a smaller white armband with a black stripe through the middle. On top of his coat, he wears a black apron that reaches down past his knees, plain apart from the red strings threaded twice through that go around his neck. He also wears a peculiar set of gloves that only cover his thumb, index and middle fingers, and black boots. Seiji is a proud and dignified individual who values Shiketsu's teachings about obligation and dignity above all else. He often stands with his arms behind his back and uses eloquent language when speaking, which causes people to refer to him as "Senpai". Seiji believes all heroes should be dignified and vulgar individuals are unworthy of becoming heroes. He believes this so strongly that he prioritized incapacitating unworthy students during the hero licensing exam over actually trying to pass the exam himself. Seiji has a lot of respect for U.A. High but believes that the students of Class 1-A sully its image because they lack dignity. He dislikes Katsuki Bakugo especially and lectured him several times during their fight about how Katsuki needs to reflect on how he represents U.A. with his actions. He is also quite obviously insecure about his small eyes. When Katsuki taunted him about it, he got angry and said his eyes were big and handsome. Seiji considers himself to be worthy of being a hero and often fails to see his own faults and has trouble reflecting on his own actions. He has clearly been influenced by Stain to reform the hero position, but he refuses to admit being influenced by a villain. A Shiketsu teacher and Nagamasa Mora believe Seiji has a tendency of imposing his value on others and has been impacted negatively by the Hero Killer. This shortcoming is what ultimately caused Seiji to fail the hero licensing exam. Even so, Seiji remained mostly unfazed and still refused to reflect on himself.