Hisako's mutant powers are weakened during a fierce battle between the X-Men and Todd, the U-Men's mad scientist.

Having defeated the U-Men, the X-Men come face to face with Yui Sasaki at her underground base, where she once ran a school for mutant children.

The X-Men mount an attack to bring down Professor Xavier's son, Takeo, before he destroys the world, putting an end to both mutants and humanity.