"Possessing outstanding reflexes, Taiki, a soft-hearted person who can't say no when it comes to being asked a favor, has participated in various sports clubs. Having finished practice in basketball club, Taiki challenges Zenjirou from the kendo club to a match, but is stopped by his childhood friend, Akari.
Then, Taiki suddenly hears a melody from out of nowhere and notices a light in the shape of a musical note. When he listens to it carefully, the voice of a boy breathing feebly is mixed within that melody. Shocked by the boy's words saying "I’m going to die soon", Taiki starts searching for the source of the voice in order to save him.
Akari and Zenjirou, who follow Taiki afterwards, witness a car crashing into the top floor of a building in the middle of town. But, somehow neither the car nor the building were damaged at all. Immediately afterwards, the car falls down towards Taiki and the others along with a digital light. However, thanks to listening to the boy's voice, they escape danger.
Furthermore, Taiki hears someone's voice saying "If you want to save the boy, then follow the guidance of the light that appears in front of you". When Taiki touches that light, called a X Loader, he is hurled into digital space resembling a cyber tunnel. There, in the Digital World, the mysterious other world, in front of Taiki and the others is an enormous Digimon, Mammon.”
