Konosuba: God's Blessing on This Wonderful World!, Vol. 13 (light novel): The Lich’s Proposal

ETERNAL LIFE CAN GET LONELY
There’s a stalker on the loose! …Or so it would seem. Apparently, Wiz has been receiving a lot of attention from a mysterious man. After some eavesdropping reveals the terrifying extent of his knowledge about her, she receives a letter requesting they meet. And when she brings it to Vanir and Kazuma, Vanir gets unusually worked up and threatens to take action! This gives Wiz the push she needs to handle the issue herself…but it looks like someone has been filling her head with weird ideas. For starters, why is she acting like a blushing bride to be?!