On Dec. 24th, 2000, the blind assassin Ryōken Hōinbō and his dog Kuro were walking along the road when Kuro happened to notice two boys who were trapped in a frozen car. Hōinbō saved the two boys, but the near-death experience had damaged their memories, and they did not know who they were. The assassin decided to take them to the nearby Happy Family Home orphanage. These children went by the names Manosuke Naitō and Sōta Sarushiro, and they waited for any sign of their real families to show up and find them. However, Sarushiro's father killed Naitō's father, and went to Zheng Fa a year later, leaving the two boys alone with no one to look for them.