I Got a Cheat Skill in Another World and Became Unrivaled in the Real World, Too, Vol. 8 (light novel)

Yuuya Tenjou pulled off what seemed impossible: He defeated the God of Destruction and saved the other world from the brink of collapse. But there's no rest for the overpowered. After returning home to the real world, an unbelievable crisis occurs--an invasion from the stars! Thankfully, conflict is avoidable...as long as Yuuya cooperates with the alien Meruru. She's on a mission to rescue her home planet and requires blueprints to a lost weapon, along with an energy source. And she's not letting anyone get in her way. Yuuya goes to the other world for a solution, searching all the way to the planet's core!