Yuki Sumi sports long black hair, a high school uniform, and was seen wearing a casual outfit at the end of LoveNow.,
While Yuki describes herself as a shy person with average conversation skills, Aqua quickly realizes this is all an act. In fact, she wants to be in the spotlight and is quite competitive, as seen in her conversations with Akane Kurokawa, wanting to gain all the attention for herself.
However, she is not a malicious person, being privately reasonable and well-meaning. 