Kazuma Satou has been constantly made fun of by his traveling companions, and the final straw was Megumin scrubbing "Holy Sword Excalibur" on his crotch. Aqua proceeding to chuckle at the size of his member was the icing on the cake. He wouldn't deal with it anymore. Revenge would be swift.

Vanir would be more than happy to help since he still secretly held a grudge against all three of his female companions. Aqua for her holy powers, Darkness for resisting him, and Megumin for blowing him up. Giving Kazuma a potion that would temporarily increase the size of his member and sexual stamina proportional to his luck. He knew exactly what to do with his newfound perverted power.

First up was Aqua. Although he didn't find her attractive, the potion caused him to grow hard on command. So when Aqua got fall over drunk, Kazuma used this time to drag her off and have his way with her face. Although she was mostly useless, he was surprised at how each pump against the back of her throat caused her to inadvertently grant him increased blessings and boosts! Kazuma may have been disgusted with himself for doing this (and for getting pleasure from it), but payback was far more important than where he stuck it in.