Kurobara Girls High School (Formerly), Asahiyama High School
Itsuki Nakano is the fifth sister of the Nakano Quintuplets. She is attributed as the "first girl" of the series. Itsuki is serious and diligent, yet she's also a glutton and crybaby.
Itsuki is a serious girl, usually getting up early compared to her sisters. She also has good manners, to the point where she cares a lot about manners. She has never been late or skipped a class, and always speaks polite language.
Itsuki has been seen to be a girl who holds a grudge, this is shown when she rejects Fuutarou Uesugi's teaching, in part, due to their earlier dispute. She is also someone who cannot be honest with herself and has a hard time being more direct. Both of these qualities often make her fight alone. Itsuki is often too precise in the timing of food cooking.
Itsuki sometimes tends to be a crybaby, whether it's due to unfavorable situations, scary things, or her stubborn self.
Itsuki has a large appetite and is mainly seen eating throughout the series. It seems like she doesn't mind treating her sisters unfairly when it comes to things related to food. When Itsuki proposes to share their cakes, Ichika suspects that his real goal is to try all the flavors. Itsuki worries about Fuutarou, but it's really because he's hungry.
According to Ichika, Fuutarou has to be firm to deal with Nino and kind to deal with Itsuki.
(Source: 5Ttoubun no Hanayome Wiki)
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