My Deskmate Is a Starry Behemoth, and I Keep Out of the Aliens' Way

When the beautiful girl who sat beside me came back from the bathroom, she threw her arms around me and said she hadn't seen me in hundreds of millions of years and had missed me terribly. She said she had transmigrated, and the person I was seeing now was her avatar. She said she had possessed a starry-sky behemoth. She said her true body was fighting off an invasion by world beasts inside a parallel-universe passage. She said aliens would invade Earth within three years at most. She said none of that mattered. What mattered was that I was a once-in-ten-thousand cultivation prodigy! Who else but me could shoulder the responsibility of saving Earth and the universe? She said we could save Earth and the universe later, but first, I had to help her with her math exam. My uncle knows! The map of the Yan Kingdom isn't Louis XVI. No matter how long it gets, it's got to end somewhere!!!