Soichiro Kiryuin

Sōichirō Kiryūin (鬼龍院 総一郎 Kiryūin Sōichirō) also known by his alias Isshin Matoi (纏 一身 Matoi Isshin) was the husband of Ragyō Kiryūin and father of Ryūko Matoi and Satsuki Kiryūin. He was a brilliant scientist and Life Fiber researcher who went on to create Senketsu, the Scissor Blades, and Nudist Beach. He was murdered by the Devil Snibal Gundam's pilot along with Nui Harime under Eggman and Ragyo's orders, impaled by his own Scissor Blade. Sōichirō had aimed to "thwart the ambitions of the Kiryūins by using the Kamui". His actions are the posthumous driving forces behind the plot of the series—including Ryuko Matoi's search for her father's killer.

Early Life
Sōichirō Kiryūin worked alongside his wife, Ragyō, in the research of Life Fibers, but turned against her after she disposed of Ryūko for her apparent incompatibility with them. Since he knew he would be punished for his betrayal, he taught Satsuki, who, at the time was five years old, about the secrets behind Life Fibers, its research and her presumed dead sister leaving her with the legacy of the rebellion against the Life Fibers. Sōichirō went into hiding after learning of the alliance with Doctor Eggman; he changed his appearance and took the name Isshin Matoi, as well as Ryūko, who was also thought to be dead, into his care. He then resumed his research on Life Fibers alongside Tsumugu Kinagase, Kinue Kinagase and Aikurō Mikisugi, and created the anti-Revocs organization known as Nudist Beach. Over the years, he developed Senketsu and the Rending Scissors to counter the Life Fibers.

Death
Six months before the events of the main story, Isshin was attacked by the Galactic Eggman Empire, who were sent to his laboratory to retrieve some important creation under Ragyō Kiryūin's orders. Knowing that, he hid Senketsu and lured Nui into stealing a Scissor Blade from him. He fought against her using them, but was eventually overwhelmed and mortally wounded by the Devil Gundam and by the scissors when Nui managed to snag them from his hands. In a moment of distraction upon hearing Ryūko's voice, Nui ended up having her left eye taken by Isshin, who split the scissors in two. Kyoto, seeing his mobile suit gone out of Control, the Devil Gundam was enraged and along with Nui, who took the scissor half used to damage her eye slashed Isshin three times before thrusting the blade into his stomach, and fled. Ryūko found Isshin laying on the ground with the other scissor half driven through his body. He told her that, if she wanted to have a peaceful life, she was to leave him there and walk away. If she wished to fight in his place, however, she should take the very Scissor Blade that was used to kill him. According to him, she would be sure to find Isshin's assailant, but a cruel fate would be in store for her. Before he could say anything else, Ryūko saw Nui wielding the Scissor Bladeand the Devil Gundam, but couldn't make out the silhouette. With the other half of the scissor in her hands, she immediately gave chase, ignoring the pleas of her father, who said he still had much to say. The mansion then exploded, with Isshin still inside. At some point before his death, Isshin sent a letter to Aikurō asking him to lead Ryūko to Senketsu.