In his younger years, he and Kuroh Yatogami were trained by the 7th Colorless King, Ichigen Miwa. He was Kuroh's brother figure and called him 'brother'. However, one day, he suddenly approached Ichigen with intent to kill and even pointed a sword at him, to which Kuroh initially stepped in front to protect his mentor. However, Ichigen stepped forward and they seemed to have a fight, although neither of them had any ill will towards each other. Yukari then left and thanking Ichigen for mentoring him well. Around that time, he joined the Green clan.
It is mentioned that during his youth, he had trouble with a relationship (the nature of it unknown) around Christmas, and hence has a great distaste towards the holiday.