Really good Sano episode. It's funny hearing Sano's reason from Anji his desire for power is just to be stronger. Sano isn't someone who is gonna list why he needs to be stronger like the average Shounen protagonist. Listen, I just want to get stronger, plain and simple. He has his reasons, which we know tie him to Kenshin.
Of course, it is interesting to learn that a rematch between Sano & Anji should be in the cards. Since he is among the 10 Swords that Shishio will use to get Kenshin's skills back to his liking. You know seeing Sano on the brink of insanity was well done and especially seeing Captain Sagara's ghost telling him enough is enough. Kenshin is the 2nd most important person in his life only behind Sagara, so he wasn't giving up. Kenshin & Sano's friendship is one you don't see too much in shounen, but it is really cool to see. Kenshin got Sano back on the right track and Sano owes it to him when he needs help.
Kind of funny how Sano was in Shimosuwa and this kind of like was a big building point for him. Anji mentioning how he grew in a week. It's something you might not notice it unless you say Sano in a day-to-day manner like Anji had. Most likely, instead of being in a rushed to get things done, he let the things come to him in an appropriate manner.