Yuudai Yamanobe is the biological father of Tomo Yamanobe and the adopted father of Mafuyu Oribe. Shortly after adopting Mafuyu, he mysteriously disappeared and only left behind a letter that states to "not worry about him". Mafuyu is very grateful to him and refers to him as "Uncle" due to him raising her as a father when her biological parents died. He is the man behind the disappearance of the Theotokos of Tsaritsyn, and it is later found that he hid it in the school lake.