Nayuki Minase is Yuichi's cousin, with whom he moves in with at the beginning of the story. She has always been in love with him (in Japan, such relationships between first cousins are legal and generally accepted) and must learn how to deal with these feelings, especially with the threat that he may fall for one of the other girls. She adores strawberry sundaes, but the mere mention of her mother's "special" homemade jam makes her sick.
Nayuki is a heavy sleeper, which has led her to collect dozens of alarm clocks; they do not work on her, but instead wake Yuichi every morning. Since she has such trouble waking up, she is always running for school and is in fact the school's star runner because of this. Similarly, she became the captain of the school's female track team despite being in her second year. She takes a long time to get up in the morning and will pass out several times during the morning before completely waking up. Despite her attempts to stay conscious, she still tends to fall asleep a lot in class.
Nayuki has a fondness for animals and never misses an opportunity to try to pet one, even wild animals, such as cats, dogs, or even the occasional fox if she can help it. Unfortunately for her, she is allergic to cats. One of her defining features is that she tends to talk slower than the rest of the characters. She will often state the obvious to Yuichi, such as when lunch break occurs or when school ends.
Nayuki is second to Ayu as the most used character in the series' marketing. Also, in both anime adaptations, her story runs at the same time as Ayu's.