Megaman ZX3 Alpha Squad, book 1: The legend return

Base of MMZXA, and what would the sequel look like without the secret ending. So the four evil Megaman are split up.

A hunter, Aku, has discover a lost underground city and went to investigate alone, meanwhile Thetis, the Ice Megaman, was on his own and went into hiding from the legion. Now two heroes must venture in a underground city, where the mystery of the legendary heroes will be reveal.

Update: I decide to use the secret ending, and I can improvise. :)