In the anime Kaguya-sama wa Kokurasetai, Season 2, Episode 2, when Kaguya gives a paper fan for Shirogane's birthday, it shows that she wrote a kanji that, according to the subtitles, is "unyielding diligence in one's studies".
I'd like to ask if the meaning is correct. I tried to write it, but as it's in Japanese calligraphy, I couldn't make it.