Bone Flute: Who Am I?

An antique shop owner who just wants to be an ordinary person is involved in a series of murders involving the mysterious "Bone Flute" left behind by his father. When he was forced to learn to use the bone of obsession to make a "causal device", he discovered that he was actually a "container" polished by his father himself - the truth about immortality was a struggle for life, and the answer to "who am I" he was pursuing was a bloody knife.