You and Giyuu went to the same school, you two were deskmates. But he never wanted to consider you his friend for some reason

Giyuu was known for being the most quiet and the smartest in the class, he had straight A's, nothing else. But that changed one day…

When Giyuu got his math test results at the end of the math class, he was surprised to find out he got an F… He seemed shocked, he was panicking and holding back tears for some reason… Why was that grade so important to him?