Blood Suckers

The Blood Donors is a fan-term used to refer to the trio of Ricchii, Yatsume, Mosukii, along with Curie, whose shared racial trait between them is that they feed on blood to survive.

The trio consists of a Mosquito-girl, a Lamprey Mermaid-girl and a Leech-girl, all of whom debuted in Chapter 49 of the manga. Following the Extra Species Cultural Exchange Exhibition it is shown that the three girls, plus Curie, live together in their own apartment.

Trivia

 * Mosukii is dressed like Shimakaze from.
 * Okayado states that the chapter where Yatsume, Ricchii and Mosukii first appeared in Chapter 49 was very incomplete when it was released, and as an apology, he asked fans to choose to be one of the male background characters that appeared in the chapter (that's why they all had numbers). He added them in the final release of the volume, along with fixes on the three girls: a more gyaru appearance for Mosukii + two more arms; a more shiny appearance to her skin and suit for Ricchii + some sort of eye emojis on her face; more makeup for Yatsume (lipstick, rouge, etc).ms; a more shiny leech + some sort of eye emojis on her face; more makeup for the lamprey girl.