Let's go with Sayaka!

Sayaka Maizono.

To be honest, he hadn't interacted with his classmate as much as he had others. Mondo and Chihiro probably knew more about her than he did, but they'd been spending less time with him lately due to...personal reasons. However, he'd already mentioned the restrictions she had to deal with, and she seemed like a potentially "safe" bet.

Still, there were some safeguards.

Sayaka Maizono will attempt to ensure Kiyotaka Ishimaru is alone before she does any sexual acts, and will wait until after class to engage in any sexual activities.

This one was a given. He didn't know how the book worked (if at all, which again- ridiculous), but if such an item did control or manipulate minds, then it'd be proper to ensure she wasn't ruined by it- or that class wasn't disrupted by Sayaka suddenly deciding to mount him in the middle of a lecture, or engaging in any other uncouth activities.

The good news was, Kiyotaka didn't need to worry about the second rule of the Sex Note, with visions of the Ultimate Idol briefly flooding into his head.

Sayaka will feel pleasure from any sexual activities with Kiyotaka Ishimaru.

Kiyotaka was not a sex-god. True, he was tall, he was lean, he was muscular, and he had a decent figure, but he'd never engaged in something like this (and he likely wouldn't, but to entertain this hypothetical, he needed to engage in multiple schools of thought that had never occurred to his "background pansexual loudmouth lookin ass", in the words of one Ultimate Yakuza.) To be fair, Sayaka likely wasn't experienced either, but the worst thing he could do here was fail to show her a good time.

.

No, the worst thing he could do here was to brainwash her into sexual activities. Again, he was just engaging in hypotheticals and contingencies.

The bell interrupted him with a screech as the doors outside began to open- the sounds of multiple students flocking in. He still had three minutes to write down what he had, but there was no telling who'd enter the classroom first.

Sayaka Maizono will be completely honest with Kiyotaka during any sexual activities.

He needed to think of more, didn't he? More suggestions, more solutions- but there wasn't enough time.

The door swung open to the classroom.