He makes Darkness a sadomasochist.

"Victory! We completed a quest without serious issue!" Kazuma cheered back at the inn. "And not only that, but Megumin, you managed to leave the alligator corpses intact enough that we got some meat and skin from them, which we can eat and sell! Bonus!"

Darkness giggled. "And I got blown up! It was awesome!"

Aqua meanwhile was traumatized as she sat in the cage in a corner, back in her normal clothes. "She won't come out, she was too traumatized by the outside world," Megumin remarked.

Kazuma stared deadpan at Aqua in the cage, and mused, "Maybe we could make even more money if we sell her off as a water purification device..."

"No wait, I'll come out!" she protested.

"I also gained a level from killing several of the alligators, but for some odd reason, I don't feel like boosting Explosion this time," Megumin mused, tilting her head, shuddering a bit as her nature as an Explosion nut clashed with Kazuma's command. "It feels... Unnatural... I suppose I could invest in a fire spell, it's pretty close to Explosion..."

"...why is your nose bleeding?" Darkness asked Megumin.

...

"What are you thinking this time Master?" Darkness asked as she sat naked on his bed, and seeing that he was holding the Note.

"Just a little something to make following the command to invest in some accuracy a little more appealing," he smirked, writing, "Lalatina will become a sadomasochist. She will derive just as much pleasure in causing pain to enemy monsters as she does in receiving it from them. She will also enjoy doing minor things to other girls like spanking them. The only one she will remain completely masochistic to is Kazuma Sato."

He then showed her the entry as it took hold, and she grinned eagerly. "I suppose that will make me more of a threat in combat," she admitted.