♡: Humiliation
Bokuto finding jerk-off instruction videos that Bokuto makes and using them to masturbate all the time to which then turns into him not being able to come unless he hears Kuroo's voice or even being told he's allowed to.
It gets even worse better when he starts listening to his humiliation series and finds himself coming so hard he nearly blacks out as Kuroo tells him how sad, pathetic, small his cock is and Kuroo can't help squeezing his giant dick imagining, his bro, Bokuto being disappointed.