Hifumi's wikipedia page: https://danganronpa.fandom.com/wiki/Hifumi_Yamada

As described by the wiki, "Hifumi has a verbose manner of speaking, often going on long-winded tangents about his interests such as anime or fanfiction. He also has a tendency to casually make creepy or perverted comments in the middle of conversations, especially about or to women. He also can't tell the difference between some insults of compliments, as shown when Toko says he smells like a "big fat ugly donkey". He doesn't know if that was an insult of or a compliment. But he also displays some intelligence, showing that he figures out one piece of Sayaka's dying message in the first trial. He also has late reactions to shocking events, as shown when Leon tries to pin the murder of Sayaka Maizono on him, and then again when Chihiro Fujsaki's true gender was exposed. He reacted calmly and interested at first, but then freaks out when he realized the situation.

Hifumi is extremely passionate about anime and fanfiction, and has little tolerance for anyone he feels has a poor or neutral opinion about them. He is passionate enough about them, that he says his dream to create a story so powerful it'll inspire others to create their own stories as well.

He refers to others in a very formal manner, calling them "Ms." or "Mr." Last Name, for example, he calls Makoto "Mr. Naegi". and Sayaka as "Miss Maizono" In the original Japanese game, he uses the honorific suffix -dono as well as their full name, for example, "Naegi Makoto-dono". This proves to be a key piece of evidence later during the trial for his murder as he mutters "Yasuhiro", Celestia's real last name as opposed to it being Yasuhiro Hagakure's first name."