As soon as she said that, Naruto began to tense; his thigh's clenched, and his cock pulsed, "Ah, I'm... gonna-"
Still smiling, Shizune let go; she watched his cock pulse for a moment in the open air, ever so close to release. She herself was unsure whether he would cum or not; and, after a few moments, he did not. Quickly, Naruto went to masturbate himself, but Shizune slapped his hand away, "Ah ah, the tests can't be administered yourself - it wouldn't be a fair test otherwise, wouldn't?"
Naruto blushed heavily, "But Shizune-san, why'd you stop? I..." He swallowed, humiliated, realising the fully nature of his situation, "I was about to fail, so why don't you at least let me release?"
"Well," The older kuniochi replied, "Why should you be rewarded for failure? Besides, this is a lot of work for me; why should I continue?" Seeing Naruto's disconsolate look, a shadow on his bright face with his bright eyes and bright hair, Shizune's smile became a grin, "I suppose I might continue," She continued, "If you're willing to do something for me,"
Hearing this, he straightened; his penis bobbed up and down with the movement, and Shizune was amused to see it move, "What sort of thing, Shizune-san?" He asked, suddenly happy again, "I can do your paperwork if you want? Maybe work for Tsunade-baa-chan for a while in your place, or-"
Shizune shook her head, "No, no; I want something relevent to this. You see, I'm going to have to continue to do this periodically until you can last, so I want you to admit your fault - only then can you begin to overcome it,"
Naruto blinked, not understanding, so Shizune continued, her grin wicked, "I want you to admit that you're a premature ejaculator,"