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 insert creepy or perverted comments in the middle of conversations.

Hifumi is extremely passionate about anime and fanfiction, and has little tolerance for anyone he feels has a poor or neutral opinion about them. Their importance of them is so deep, Hifumi has said it's his dream to create a story so powerful it'll inspire others to create their own 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". 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.

Although having a somewhat misanthropic look on society, Hifumi will not stand for indecent crimes against those he holds in deep regard, and even went so far as to kill Kiyotaka to avenge the harm he believed he had done to Celestia.