Dia is a very refined, polite and mature young woman who speaks in a formal style of Japanese, regarding all of her friends with politeness by referring to each of them as "-san", and usually ending her phrases with "-desu wa." Strict, hardworking, and a bit of a perfectionist, she dislikes it when things are done sloppily or incorrectly, which is part of the reason why she initially rejected Chika's application for a school idol club. She is very meticulous regarding small details, as far as going on tirades regarding the unorthodox reading of certain Kanji.