Edge training

You sneak into his room in the morning. He is still asleep. You don't wait for him to wake up, you just sneak under his sheet. You take his member into your mouth, it hardens almost instantly.

"What?" he wakes up "Emily?"

"Hello brother" you say "I have an idea. We need to get you a better stamina" you stop for a moment to give his cock few sucks "so you are forbidden from cumming, but you can jerk off. I would even encourage it, the more the better. You can think" you are giving him handjob while talking "about my body for example."

"But" he gasps feeling your mouth on his dick "I will be so pent up that I'll cum quickly again."

"Maybe in the beginning. But with time your body you would learn to understand that instant gratification isn't a way to go."

"Emily, I'm gonna..."

"Oh no, you don't!" you immediately stop all stimulation. After half a minute you quickly bring him on the brink of the orgasm again. After you do it for a fourth time he looks like he's gonna cry, but you have to be harsh "do it five times during the day. We'll meet in the evening."

In the evening you two meet. He looks totally desperate.

"Emily, please" he pleads "I have to cum. I'm gonna die otherwise."

"Didn't you want me to teach how to please girls?"

"Yes, but please, I can't take it" he sounds like a whiny child.

Giving him pleasure would be a bad idea, it would teach him that by pleading he can get what he wants and it would work against your goal to make his stamina better. But he really sounds desperate. Maybe there is a place for compromise?