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|“||Although we are weapons, we are not slaves. And I refuse to be livestock. We, ourselves, are the masters of the laboratory that produced us.||”|
Yotsuba Genzou (四葉 元造) was the first Head of the Yotsuba Family, which is one of the Ten Master Clans. He is the father of the twins Miya (深夜) and Maya (真夜), and the Shiba sibling's maternal grandfather.
Appearance and Personality
Genzou was a man who valued his family and clan immensely, going as far as wiping out approximately 4000 individuals in Dahan in the name of revenge for kidnapping his daughter, Maya (leading to Dahan's collapse). He has been shown to hold some guilt when his clan members were killed during their operation in Dahan despite them all being volunteers. He showed regret when he was at his limit, that he wouldn't be able to see his daughters again.
Genzou believed that each member of the Yotsuba Family could eliminate no more than 120 of the lives of Dahan government officials, magicians, and researchers. Thus, he forced himself to continue the revenge to reach at least the number so that it would be fair to others that have sacrificed themselves to aid him. This also shows how he was a man with dignity, suiting his role as the head of Yotsuba.
During AD 2062, Genzou's daughter, Maya, was kidnapped by the Kunlunfang Institute in Dahan and was experimented on. In response, he decided to avenge his daughter by eliminating everyone connected with the Institute. With the support of the rest of the Yotsuba Family, around 4000 Dahan individuals were slain in exchange for 30 Yotsuba Family members, which was half of the clans fighting strength. 
Grim Reaper (死神の刃) is an Outer-Systematic Mental Interference Magic unique to Genzou. It plants a specific image within the target's mind, usually one of death. After the target has been exposed, no form of protection, or distance, or time will stop the magic. As long as the victim recalls the image, the implanted suggestion will take physical form. Enemies who meet Genzou for a second time would kill themselves. The implantation process does not require a direct meeting, but the final kill does require it. The target has to be aware of the user and the user has to be aware of the target. The only way to survive is getting rid of the memory of the image.