Mega Man Battle Network 4

Lan and MegaMan partake in a series of net battle tournaments. Depending on the version of the game, different opponents and scenarios will occur. In between tournaments, a criminal organization called Nebula will attack. They spread corruption with the use of dark chips. These are battle chips infused with the power of darkness. They grant immense firepower compared to a regular chip, but spawns a dark soul and does a small amount of permanent HP damage into the navi that uses it.

Meanwhile, an asteroid was travelling through space, heading for Earth. The scientists at NAXA (ANSA in Japan) attempt to divert it. When their laser strategy failed, they decided to send a net navi into the asteroid's cyberworld and change its course. The navi was chosen through an international tournament, which Lan and MegaMan ended up winning.

Nebula attacked again, but MegaMan was able to delete the head navi and reached the main program operating the asteroid. The program was called Duo and was planning on destroying Earth because of the high levels of dark energy. Lan and MegaMan proved through battle that all people had the ability to conquer their inner darkness, and successfully averted destruction.