Chiaki normally has a quiet and sleepy disposition, but she becomes a lot more lively when discussing games and concentrates hard when playing. She often uses gaming terms and game references. She has a number of unusual habits, such as dozing off while playing games and taking long pauses during her conversations to think about everything she wants to say. She sometimes even sleeps while standing and forgets to breathe when she's playing games.

Chiaki is very calm and she once mentioned that she has never screamed. She often helps Hajime Hinata during Class Trials and provides important points. She can be stern and bluntly honest, at times forgetting to take other people's feelings into consideration.

Chiaki usually ends her sentences with a negative note even though she actually means to compliment someone or cheering someone, such as "...I think", or "Maybe...". Hajime once said that sometimes he wishes that Chiaki would end her positive sentence on a positive note.

Chiaki truly cares about and wants to protect everyone. She dislikes killing more than anything and she gets very serious about the topic. She is understanding towards Nagito even though his actions frustrate her.

[Spoilers] In Elevation, Nanami has two different personas - her AI and her "real life" self. In real life, she has gone through trauma that has made her unable to trust most people, and she is withdrawn. This will change as the story develops and she has the chance to grow.