I Quit Guarding Demon-Sealing Tower

Charlie guards the Demon-Sealing Tower for 1,000 years, holding back three top-tier Beast Kings and hordes of Soul Beasts that all tremble at his blade. The Sky Kingdom royal court frames him as unfit for the post and forces him to abandon the tower. Half a day after he leaves, the tower shatters, and billions of Soul Beasts flood the Human World.