Final Fantasy X is the tenth installment of the Final Fantasy series. The game is by right owned by Square Enix(during that time it was called as Square Soft). Zahasuki Harikuni liked Tetsuya Nomura's(graphic designer and director of several Final Fantasy series) ideas of the main characters being able to upgrade their stats solely instead of leveling up to strengthen them.
There are few very inspiring features in Final Fantasy X that made Zahasuki very intrigued of implementing them in School Fare. Some are quite obvious, while others are rather 'shadow of their facade'.