Hiiragi is the best assassin in all of Japan. He serves under the white king and at one point was sent to kill "Tatara". He also taught Shuri, Asagi and Shido how to fight. Hiiragi is said to mean holly, and his victims are often sent holly as a warning that they are about to meet their end at Hiiragi's hands.

Spoiler

Hiiragi was put in charge of the invasion of Awaji Island by the emperor. He was tasked with killing the current leader and bringing Ginko back to Kyoto. Although he accomplished both, he has never been able to forgive himself for hurting the white king so deeply and as penance, he now serves her unquestionably. Hiiragi is also the only person who understands how Ginko, the white king, really feels. In fact before her arranged marriage, it is hinted that he loved and continues to love her. Eventually Shuri and Nakijin are able to defeat him in battle, a battle that costs him his arm. He is finally defeated by Asagi and dies along with Ginko when the palace falls in upon itself.