Taiki Goes to Another World!

Japanese Name: 
タイキ、異世界へ行く!(Taiki, Isekai e Iku!)

Due to his superior athletic skills and his inability to refuse a request, Taiki takes part in a various number of athletic clubs. After he finishes practice in the basketball club, Zenjiro from the kendo club challenges him to a match but this is stopped by Taiki's childhood friend Akari. Around that time, Taiki hears a melody that seems to be coming from nowhere and sees a light shaped like a music note. As he strains his ears, he hears the breathing and feeble voice of a young boy mixed within the melody. Surprised by the boy's words that he is "going to die soon," Taiki begins to search for where the voice is so he can save him.

Akari and Zenjiro chase after Taiki, witnessing a car crashing into the top of a multi-story building in the middle of the city. However, neither the car nor building are damaged in any way. Immediately after that, the car drops down towards Taiki and the others along with a digital light. However, by listening to the boy's voice, Taiki and the others are able to escape from danger. What's more, an unknown voice tells Taiki that if he wants to save the boy, then Taiki must obey the guidance of the light that has appeared in front of his eyes. When Taiki touches that light called the X (cross) Loader, he is swallowed up by a digital space shaped like a cyber tunnel. There, in the strange other world of the Digital World, a giant Digimon - Mammon - towers over Taiki and the others.

Source: With the Will Forum Topic