Japanese "hate" towards the Chinese is very very recent, and only mainly a thing during imperial Japan in the late 1800s to 1950s or so when Japan was more modernized and developed than China, which was more poorer and less modernized.

I'm pretty sure the average Japanese civilian never hated or cared about the Chinese. It was only the occupying forces (the soldiers) who were taught and trained to hate the Chinese. It's all part of "hardening" the soldier, to make them ruthless against the enemy, who was the Chinese at that time, to see them as less human, so they can succeed in their goal of conquering China.

Idk what writing system has to do with hate? It's just symbols meant to represent things. We use Arabic numerals, and yet that doesn't stop many Americans from hating the Arab world?

Nowadays, there's no hate between the East Asian countries, except some individuals, and China nowadays is more powerful and developed than Japan.