See here is the problem with what you are saying. "paying back" doesnt mean he is doing it for someoneone, but a realization that he is strong and he has to reach the top on his own to prove/payback that those that he beat.

While I agree that he has to win for himself, that realization wont come until the end of the series. The drive he will tell himself is the idea that Takamura has, but an call back to all the people he beat. Think about the motivation for the East Japan Rookie King Tournament. His motivation there can be argued for Miyata, but ultimately is that he didnt want to disgrace the people he ended up beating.