Sho Yamato is a boy who enjoys MTB (short for "mountain biking") a whole lot. He's always practiced at the "X-Zone" (a place which his dad Takeshi made for MTB) with his friends Kakeru and Makoto while riding on a bike his dad has built called "Flame Kaiser". One day, he was challenged to a race by a MTB team called Team Shark Tooth and whoever won the race will get the X-Zone. During the race with Team Shark Tooth's leader Gabu Samejima, black smoke suddenly covered the ground around them, and they were sent to another world that's also called the "X-Zone."