Well, might as well help Megumin blow off some steam... And him.

Kazuma found himself following along behind Megumin as she explained to him, "I shall need you to accompany me. If I don't let off an explosion at least once a day, I just don't feel like myself."

"Sure, that I get, but why do you need me to accompany you? Can't you do this yourself?" Kazuma asked.

"Then who would drag my spent carcass back home?" Megumin retorted. "Aqua has to work off her tab, and Darkness went off training for a bit."

Kazuma nodded and groaned. "Fine, but you're blowing me when we get to the location you want to blow up," he said. "And before you let off the spell too, so you still have the energy. Every day we do this."

"Fine," Megumin pouted, puffing her cheeks out cutely. Eventually, they settled on an abandoned old castle, and Kazuma sat down as Megumin got on all fours and crawled over to him, fishing out his dick. Without any preamble, she took it into her mouth and bobbed her head furiously, clearly impatient to get it over with, so she could let off her blast, once he had let off his. And internally, she had to admit, she wanted another taste of his seed.

He moaned in pleasure, letting her do so this time, and just relaxed and enjoyed it. Before long, he came, and filled her mouth once more. She got up after swallowing, grabbed her staff, and sent the explosion spell off at the castle without any further delay. It went off in a spectacular blast.

"Points for sheer destructive power!" Kazuma complimented as he had Megumin on his back and they walked home.

...

"The hell do you mean we're not under attack!? That blast hit the castle directly!" the current resident was demanding of his undead servant, who was currently explaining that the culprits were leaving. "...fine, whatever, so long as the pest has gone!" he huffed, returning to whatever he had been doing before.