@Jacough From my understanding, Japanese passing grades are different from western standards. I think you just need to get above half the average of the student body to pass. For instance, if the average is 50, then you would need half that grade or above to pass (so a 26 would pass, 25 would be barely passing, and 24 would be failing).
Not sure if I am fully correct, but anyone can clarify if I made any mistakes... haven't attended a Japanese school so I'm not fully sure.