Make Kazuma into a perverted dom and give him the Note.

Darkness stowed the Note for the time being, and finished the job, though all she managed to really do was act as bait for Kazuma to catch a bunch since none of her attacks hit, but he still caught enough to get some decent money.

...

"How can boiled cabbage taste this good?" Kazuma was asking, having kept a few of the catches to eat themselves.

There was a brief discussion on how they had all done, before Darkness turned to Kazuma and smiled. "Thank you so much Kazuma! You saved me when those cabbages were ganging up on me... though you could have let them go on a little longer," she mumbled the last part.

Kazuma stared for a moment, before Aqua cut in to welcome Darkness into the party, which triggered an argument over her making a unilateral decision. One thing led to another, and she tried to hold their payment hostage, and Kazuma tried to steal it back with the skill Chris had taught him... And ended up with Darkness's bra somehow. As Megumin and Aqua called him a cad, he protested frantically, saying he had no control over what he snatched with the skill.

"I knew I loved this party!" Darkness swooned. "Hide behind me any time you want!"

"Damn it..." Kazuma groaned, caving into the pressure.

...

Later that night, Darkness took another look at the Sex Note, the idea of it being a fake magic item never crossing her mind. She got a quill and considered what to write... Kazuma was nice enough, but just a bit... Too nice... But she could easily fix that... Make him more domineering towards her...

Of course, she'd probably have to use her real name... Oh well. So she began to write, "Kazuma Sato will become an unrestrained pervert, willing to indulge in all of his fantasies. He will also become a dominant in sex. He will come into the room Lalatina is staying in, and upon her showing him the Sex Note, will use it to make her his sexual ****, unable to resist his every command."

She set the Note down, giddy as she waited.