Reina Sera

Reina Sera (血清レイナ/on the right) is one of the side characters of the series, and one of the nicest people in it. She is very athletic, being one of the best in Hisui's classroom in sports. She even rivals the best boys in the classroom. She is not very confident in herself though, having once messed up in Middle school during a sports festival. She transferred to Seidou Academy from Aishin Middle School, a private Catholic all-girls school. She is also the only girl among the first years to transfer there from Aishin. In appearance, Reina is short, slim, and a bit short-haired. She also has a bust equal in body proportion, but not size, to Rangetsu. She has brown hair and eyes.

Reina is very religious, therefore she keeps any hidden desires to herself, as to refrain from sin. This causes her to be very shy towards people, though this does not stop her from making friends. She does not have a lot of confidence in herself either. This is proven in all volumes of the series. The first instance was the moment she was selected as class representative for the first years in Jyuri's classroom. The second instance was her lack of resolve during the rooftop scene. There are more, but the point is she lacks self-confidence. This does not stop her from falling in love with Hisui at first sight. Therefore, she ends up heartbroken when she believes that he and Rushella have a relationship, and to make matters worse for her, she has to compete with Mei and Kirika for his attention. Luckily, he would rather give it to her than any of the other girls in the series, but he doesn't get that luxury.

Reina learns of Hisui's secret life and she also learns of the identities of the girls around him in Volume 4, but she never brings this up in Volume 5, probably knowing that he does not want to be reminded of the horrors they both experienced for her to know. She has also been bitten by a vampire, specifically Kishida, but has refrained from transforming, though she does not become a vampire. People like her are easy targets for vampires, due to virgin females under 18.

She first appears in Volume 1.