A story of a paralyzed, terminally ill man reborn in another world, slaying all and conquering the world with his sword. Though he dies, his chivalrous spirit remains, worthy of being a hero of the world. Who can write of your deeds, as you spend your old age studying the profound mysteries of the universe?

The world of Long Summer is shrouded in eeriness. Every six days, on the seventh day, this strange entity invades the dream realm, releasing its malevolent forces to affect reality. On this particular day, an unusual murder case in Kuroki City leads to the discovery of a mysterious girl. She possesses the Eye of Truth, which allows her to see through illusions on the seventh day.