The No. 1 most skilled and popular, deadliest eldest son / The ultimate weapon of the Yozakura family with the highest intellect and combat power among the seven siblings. The eldest son of the Yozakura family. His affection for his siblings is abnormally strong, and his love for the third daughter, Mutsumi, is so extreme that his family treats him like a pervert. He cherishes Mutsumi excessively and often picks fights with Taiyo, who receives special treatment from her, but he seems to acknowledge Taiyo's grit. His favorite weapon is the thread-type weapon passed down through the Yozakura family, "Steel Spider." Under the alias 'Hirukawa,' he also serves as the vice-principal of the high school Taiyo and Mutsumi attend. He is a severe siscon, specifically for Mutsumi. Despite his attitude, he acknowledges Taiyo as his brother-in-law and family, protecting him even at the cost of his own life. His Blooming, revealed in the fight against his father Momo, is 'Void.' His Blooming first manifested only four years ago, which is considered late among the family except for Taiyo; this is said to be because Kyoichiro was already so strong that he had no need to Bloom. Though he is only 21 and still young, as the eldest son, he shows a more mature side than his peers. It seems he also has an obsession with Guest, similar to his feelings for Mutsumi.