Question

what was the actual reward for sadao hoki​

Answer 1

The actual "reward" for Sadao Hoki was the escape of the PoW (Prisoner of war)

Reason :-

Though he was Japanese, still he wanted to help the PoW to escape. Therefore, he listened to his heart and helped the prisoner to escape. And when the prisoner escaped, Sadao was very happy. That's why the escape of the PoW was "reward" for Sadao Hoki.