Eleven-year-old Satsuki and her little sister Mei move into a historic country house with their dad and experience the magic of the Soot Sprites, and the world of Totoro, a magical forest creature.

MegaMan's fiercest enemy, Bass, is back and stronger than ever. He has fused with CyberBeast Grave to become DenTech City's worst nightmare. To save the day, MegaMan must fuse with ProtoMan using the Soul Union program. Together, they may have a chance of defeating their archenemy.

When trouble returns to DenTech City, the authorities turn to the fifth-grade hero, Lan Hikari and his NetNavigator--MegaMan. Bass--an unrepentant delinquent with the ability to mimic the power of any opponent--has arrived in the synchronized duo's hometown. This is very bad news for DenTech City: how will MegaMan be able to defend the city against a foe as powerful as himself?