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)

Krul Tepes is the third progenitor among the vampires and the vampire queen of Japan. She is responsible for turning Mikaela Hyakuya into a vampire. Being a Vampire, she is far stronger than a Human and being a Founder among the vampires, she is capable of easily defeating other vampires. Just like all other vampires (minus Mikaela), she views the humans as nothing more than livestock. She sees them as foul and endlessly greedy creatures who will do anything for their own personal gain. When Ferid Bathory slaughters the Hyakuya Sect orphans she carefully hid in Sanguinem and protected as livestock, she becomes enraged because he fatally wounded one of the seraph and allowed another to escape. She never mentions a word about the orphans and displays no interest in them. She saves Mika's life against his will by turning him into a vampire, but this appears to have been done for her own personal interests. He refuses to drink human blood, so she gives her blood to him in exchange for making him dependent on her. Even so, she is the only vampire who shows him kindness, and there are several moments when she hugs him or treats him gently. After developing a close bond with Mikaela Hyakuya, she shows concern for his family member, Yuichiro Hyakuya. She claims to like both Mika and Yu. However, it is uncertain if this is because she is close with Mika and is concerned for Mika's sake or if this is because she wants to use the seraph for her own purposes. She also appears to trust Mika, and only she and Mika appear to know Krul's true goals. (Source: Owari no Seraph Wikia)