This is book number 16 in the Konosuba (light novel) series.
P.S. PLEASE LOOK FOR ME.
With Serena’s sudden rise in popularity, Aqua’s insecurity sends her fleeing from town, leaving only a letter behind. If they no longer need their goddess, then Aqua won’t stay where she isn’t wanted! She’ll beat the Demon King by herself, save the world, and return to the heavenly realm! Little does she know, though, that the people of Axel are nothing without their beloved mascot—not that Kazuma plans to do anything about it. He’s only Level 1, after all. Oh, who is he kidding? With this latest development bringing him straight to the Demon King’s castle gates, it’s time for Kazuma to rally the troops, power-level like never before to awaken his hidden potential, and get his goddess back!