Test the serum both directly and 'indirectly"

Tsunade watched as Naruto's eyes glazzed over completely and decided to begin her 'tests' "Okay Brat, now I'm going to start testing the serum's effect, just to make sure everythings going right" said Tsunade as calmly out on some rubber gloves to appear 'professional' to Naruto before gently taking hold of Naruto's stem and balls stroking and squeezing them "how's that brat, still reacting like before?" asked Tsunade with a slight smirk on her face behind Naruto's back "uhh... not really it still feels good but not as strongly as before" he responded slowly, "good that means the serum's working" Tsuande remarked feeling Naruto become hard slowly but surely before letting go, to his muted disappointment.

Tsuande laughed lightly "don't worry brat you'll feel good soon enough but for now lets check if... indirect methods react better or worse than before" said Tsunade "what do you...? *sigh* whatever Granny, if you say so..." slurred Naruto resignedly as he blinked blearily. Tsuande smirked at how agreeable Naruto was now musing 'I should have done this ages ago then I wouldn't have gottten nearly as many headaches from him; ah well, better late then never' she decided before using her chakra to make her finger properly lubed before lightly storking Naruto's asshole "G-Granny what a-are you doing" Naruto asked before moaning at the end as Tsuande added more pressure to her finger lightly pressing inside of his hole "just checking any stimulating areas to see how they were affected by the serum, hmmm seems this area still sensitive what do you think Naruto" Tsuande asked as she began to push her finger into him "oohhh mmmgh G-Grannnyy..." Naruto moaned out showing just how sensitive his ass had become to Tsuande's amused and lustful glee.

"That so, well we're going to have to throughly check just how sensitive you are so I know how to fix you properly" Tsuande commented smirking as pushed another finger into Naruto and began to finger his ass firmly leaving him a moaning and keening mess under her ministrations "ohhh Granny, d-do whatever you want, just don't stop" Naruto groaned out to out of it to really understand what he's saying "oh I intend to brat don't worry about that" Tsuande chuckled menancingly as her cock throbbed to Naruto's moans. Tsuande leered at Naruto with undisguised lust as she brought him to orgasm with only two fingers, and she was only getting started with her 'Tests'.