She decides to punish Sakura for how she used to treat their Master.

"So Sakura, tell me, how many times did you hit our Master in the past?" Hinata asked with a devious grin.

"About... 43," Sakura confessed nervously.

"Alright, then go put your hands against the wall, and stick out your ass. I'm going to spank you 43 times," Hinata ordered, getting into it.

"Yes Mistress," Sakura whimpered, obeying and presenting her ass for Hinata to punish.

Hinata grabbed her headband and walked up behind Sakura. "Every time I strike you you are to apologize to our Master, understand?"

"Yes MistRESS!!" Sakura yelped as Hinata swung the headband, striking her butt with where the cloth covered the metal. "I'm so sorry Master!" Smack! "Please forgive me Master!" Sakura pleaded.

"Alright Hinata, just don't do this for any future hits if I kinda deserve them," Naruto told Hinata as she continued.

Hinata nodded, but said, "No promises for the undeserved ones, given you still have the same friendship outside of sex..."

Naruto chuckled as they kept going. The final blow came with a THWACK! "I've been such a bad girl Master..." Sakura moaned, her ass red, and her pussy quite wet. Letting her Mistress punish her before their Master had turned her on.