Knowing Hinata is not as good in neither hand to hand combat nor ninjutsu as her peers, Kurenai diverged an alternative training plan for her to survive and escape "hard" situations.
Hinata was only sucking the tip at this point as the aroma of the man encompassed her ol factory. She tries her best but Kurenai knows it isn't enough so she asked the man to force his dick down Hinata's mouth regardless if she was ready or not. She has to endure this training 3 times a week until she masters her new self-defense techniques