Sycore_w
He should try to learn the secret jutsu of the clans in the village. Before he goes back in time, he should try to break into certain clan’s jutsu library. If you get caught, jump back in time. Keep trying every reset. Eventually, using seals or something, you should figure out how to acquire the jutsu. Mind-related jutsu from Yamanaka, Shadow Manipulation, etc. Being able to extract memories, secrets, and jutsus from opponents forcibly would be worth it. Using shadow manipulation to control someone’s body to force them to run into a preset seal trap would be useful. With mind transfer jutsu, could you force them to do suicide techniques like Dead Demon Consuming Seal without risking your soul? But forcing the Shinigami to take the enemy’s soul because you're using their body to cast it? If so, you’ve got a combo that can take two powerful enemies down at once.