Yuki's personality was not shown.
At some point in their life, they were picked up by the Brotherhood of a Thousand Nights, a religious organization infamous for cruel experimentation on orphans.
Events of 2012
The orphans move out shortly before the vampires destroy the Hyakuya Sect.
One of the children living at the Hyakuya Orphanage in Shibuya with Mika, Akane, and Yuki back in 2012 prior to the Apocalypse. Miyuki Yamada (Mahiru Hiragi) "adopts" him when he is four years old, and Mika has to calm him down before he leaves.
A member of the Hiragi family who adopted Junji from the Hyakuya Orphanage for experiments while using the alias of Miyuki Yamada.
Mika's second-in-command and the elder-sister figure of the orphans.
The charismatic leader of the Hyakuya orphans.