One of the top expert killers, tired of endless assassinations and having survived a cruel and suppressed life, decided to escape the world's strictest assassin organization.

A chance came during one of the nights when the organization was least prepared, and he fled. However, he discovered that the night he escaped was the night when the organization had sent out many experts and ability type users to capture a phoenix weakened by its rebirth. Eventually, when surrounded and knowing that his situation was hopeless, he desperately shot at the ability user blocking his way. This helped the phoenix break out of the encirclement and grant him his one and only wish – freedom.

The assassin's soul was sent back to his ten year old self. He woke up at a point in time that would allow him to drastically change his fate – he killed the two assassins that picked him up and brought him to the organization.

Thus, he began a brand new life.

Two naive little girls and one experienced boy living together and filling their days with warm memories of childhood…