Yuno Gasai is a young girl with pink eyes and long pink hair that she wears in pigtails, two hanging as frontal locks featuring a pair of red bows, and the back pigtails are left bare. Her most common attire consists of blue shirt with a ribbon on her chest and blue skirt with high socks.
Yuno's personality is an ambiguous one, for the most part she is a sweet, feminine and sometimes shy girl when around Yukiteru. This masked her darker side that is of a ruthless, cold and calculating psychopath who has little if any problem in using others for her ends, that is her and Yukiteru's survival. She will resort to cruel and mostly violent methods that most of the time end in bloody deaths, of either the Diary Holder or any follower, effectively making her a Yandere.