For those ten days, Naruto rarely ventured out of the Uchiha Clan Compound.
His Shadow Clones handled most of the minor errands.
Sasuke, meanwhile, went to Kakashi for special training every day.
What surprised Naruto was that he had heard nothing from Jiraiya since they parted that day. He had no idea whether the man had left Konoha or was gathering material at the various hot springs.
On the last day of Sasuke's special training.
At a Secret Training Ground in Konoha.
"Chidori!"
"Whoosh... bzzzt!"
Bang!
Sasuke had completely mastered Chidori, a ninjutsu ranked at least A-Rank, after just ten days of special training. Kakashi found it hard to believe; developing this technique had taken him a very long time.
As expected of you, Sasuke. Three days to learn Chidori, five days to coordinate it with the Sharingan for a high-speed thrust... and ten days to unleash it instantly without hand seals... am I getting old?
With that thought, Kakashi walked over to the stone pillar with a huge hole punched through it and examined it carefully.
"Hmm... judging by this degree of damage, Sasuke, you can use Chidori at most ten times in succession in a day. Of course, if Naruto is with you, you can use it more often."
Sasuke's right hand was completely numb. Repeatedly gathering lightning in his palm had left the once-delicate skin damaged and creased.
"Because of Naruto's Medical Ninjutsu?" Sasuke asked quietly, slowly bringing his panting under control.
"That's right. Naruto's healing technique isn't ordinary ninjutsu. It's the Mystical Palm Technique, and only a handful of people in Konoha have mastered it."
Seeing the anticipation on Sasuke's face, Kakashi said bluntly, "Forget it. Medical Ninjutsu isn't like Chidori, which you can learn step by step as long as you have lightning release chakra.