Has her hold him after class for a talk, and give him a blowjob.

"Byleth Eisner will ask to see Sylvain after class, implying to want a word about his conduct, but once they are alone, will lead him to an empty classroom where they won't be disturbed, and give him a blowjob, eager to do so," Sylvain wrote in the Note.

Mentally scoffing, he stowed the Notebook away, and was about to resume taking notes when... "Oh, and before I forget... Sylvain, please stay after class, we need to talk about your... Behavior in the week since I got here," Byleth spoke.

Of course, no one batted an eye, except for Sylvain, who was stunned, and sputtered in shock. "I dunno why you're acting surprised," Ingrid noted to him. "You're long overdue for a lecture."

'This can't actually be real, can it? Yeah, this could easily be a coincidence, I do have a reputation for questionable behavior, that's gotta be it,' Sylvain was thinking frantically, but even as he thought about it, he had to admit the timing was bizarre... Still more likely to be coincidental, but maybe...