He first appeared in chapter 36, along with Lily and Yukihina. His next appearance was in chapter 41, during the battle at the research center, where he caught Toki’s bullets that were aiming for "The One Being Sought" and stated that he had seen a similar face in the past before sending the bullets back at the Code:Breakers. Following Heike’s arrival, he retreated inside the building with Yukihina and "The One Being Sought".
In chapter 43, he attempted to kill the Code:Breakers by throwing several metal beams on them but his attempt was foiled due to Toki’s magnetism. When Toki asked him how he knew him, Sendou replied that he had no words for a weakling and was seemingly crushed by several metal beams launched at him by Toki. However, he emerged unscathed and proceeded to turn invisible, assaulting Toki from various locations and knocking him down with his punch. When Lily begged him to help her, Sendou simply stomped her arm, stating that "he" had no use for Lily and had assigned him to punish her in case of failure. He then attempted to kill her with his iron fist, stating that she was a useless poison woman who didn’t deserve to live, only to be stopped by Sakura. As he tried to attack them both, he was kicked on the face by Toki, who attacked him by manipulating hydrargyrum. Sendou mocked Toki for playing with water and turned invisible again, going for a surprise attack. Much to his shock, however, Toki elbowed him in the stomach, having used the hydrargyrum on the floor to track Sendou’s position.
As he tried to attack Toki again, he was enveloped by the liquid metal, which restrained his movements. When Toki asked him where he had seen his face before, Sendou responded that in the past battle between the Code:Breakers and the Re-Codes, he had seen a female Code:Breaker with the same heterochromatic eyes. After Toki questioned him about the identity of her killer, Sendou laughed, stating that he was Re-Code:03 and that Toki could never defeat him. He proceeded to break free of the hydrargyrum by using the heat from his skin and punched a hole in Toki’s stomach, declaring that justice is strength and the victor sets the rules and that he would claim the title of Re-Code one day. However, Toki was still alive (having replaced himself with mercury) and used his magnetism to pull out the mercury vapors Sendou had inhaled from inside his body. Sendou attempted to beg for his life and then launched a final attack at Toki, but was shredded from the inside out by the mercury balls before he could do anything and died.
Blackout: By changing the texture and color of his skin, Sendou can camouflage himself, becoming essentially invisible.