天人之血 Ancient Relic

A boy named Alvis has been forbidden by his adoptive mother Sheena from leaving the forest where they live, for reasons unknown to him since childhood. But Sheena promised Alvis that she would explain everything on his sixteenth birthday. Today is that day. Reluctantly, Sheena finally prepares to reveal the truth — but at that very moment, a group of uninvited strangers clad in red comes bursting through the door...