Leechi

Ricchii is a Leech. Originally participating in the Inter-Species Cultural Exchange Exposition looking for a host, she eventually wound up sharing a residence with three other blood-sucking Liminals.

Personality
Ricchii is a happy-go-lucky person who enjoys having fun, eating and swimming. She is pretty uninhibited and doesn't show any embarrassment when going around the shared house and swimming in the attached pool completely naked in full view of her housemates (principally because she finds her Exoskeleton Suit stiff and annoying). She may also have an exhibitionistic side, freely admitting to her female housemates, Mosukii and Yatsume, that she is a hermaphrodite and happily showing them her erect male genitalia when Yatsume expressed interest.

Even though she is partially male and partially female she shows to have a feminine personality and actually considers herself more as a girl rather than a male (this is also spread to her sexual tastes since she shows to have preference for boys) since her whole body looks like a female one and she is able to retreat and use her male genitals when she wants. Her favourite blood type is "Refreshing but thick"

Skills & Traits

 * Leech Physiology:
 * Hermaphrodite: Leeches are hermaphrodites; which means they possess both male and female genitalia (the female vagina, womb and ovaries, and the male penis and testicles (which are held within their bodies near the ovaries)). With both genitalia being fully functional, a leech can use their penis to mate with female beings and impregnate them or use their vagina to mate with male beings and become impregnated. It is unknown whether a leech can become impregnated from their own sperm but they can become impregnated by the sperm of other leeches.
 * Storage Mode: When not erect, a leech's penis is kept retracted within their vulva, presumably acting in similarly appearance, size, function and location to the human clitoris. When aroused the penis grows in size and extends out of the vulva into a rigid form to enable its use in penetrating during sex. Yatsume nickname's the aroused form of Ricchii's penis "Battle Mode".
 * Boneless Form: Due to possessing no internal skeleton, Leeches do not possess traditional humanoid arms and legs (and by extension toes and fingers), instead they possess tentacle appendages that mimic the appearance of humanoid appendages. Since they posses no bones, they wear a rubber suit with a skeletal structure inside it in order to mimic bones and appear more humanoid. While not wearing this suit, they can collapse due to having no bones. It is shown that Leeches are sometimes uncomfortable while wearing the suit and sometimes prefer to have a break from "having bones" through practising nudism.
 * Suckers: To hold their prey, Leeches possess strong suckers on the end of their appendages which ensures that their prey can not get away until the Leech is done feeding or mating. Their suckers also enable them to climb walls and ceilings with relative ease.

Possessions

 * Exoskeleton suit: Due to her lack of a skeleton, Ricchii is forced to wear a special suit with a built-in exoskeleton when moving on land. However, because she considers it annoying (and prefers swimming nude anyway), she takes it off whenever she has the chance.

Plot
Ricchii was working at the Inter-Species Cultural Exchange Exposition as a waitress serving artificial blood juice which she claims is a special recipe of her people.

Zoological Classification
Leeches are a pseudohuman species of invertebrate beings that have evolved to possess forms similar to humanoids. Similar to their animal counterparts, leeches are humanoid Annelids whose diet consists of feeding off of the blood of other beings. To do this, Leeches possess sharp teeth used to penetrate the skin of their prey and an anticoagulant enzyme in their saliva ensures that their prey's blood won't coagulate (dry up and solidify) while they are drinking it.

Leeches have aided medical science as far back as the ancient Greeks where they were used to aid in bloodletting. In modern times, Leeches help in procedures such as the reattachment of body parts and reconstructive and plastic surgeries and, in Germany, treating osteoarthritis.

Trivia

 * Despite being a leech, Ricchii's appearance (particularly the head shape and stripes) is closer to that of hammerhead worms, which aren't bloodsuckers (though they are also hermaphroditic). This contradiction is owed to the fact both species are called hiru (ヒル) in Japanese.
 * Ricchii's nipples are inverted. Inverted nipples are a natural condition where the nipples, instead of pointing outward from the breast like most average nipples, are retracted inside the breast. As natural as having an "inny" belly button or an "outy" belly button, inverted nipples will harden, grow and 'pop out' just like an average nipple when stimulated, aroused or cold, and return back inside the breast aftward. Inverted nipples will also grow and protrude from the breast like an average nipple during pregnancy and breastfeeding. According to a study, about 10% of all nipples are inverted.
 * Ricchii is the second character in Monster Musume to possess inverted nipples; the first being Suu.
 * Okayado states that the chapter where Yatsume, Ricchii and Mosukii first appeared in Chapter 49 and Chapter 50 were very incomplete when they were 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).
 * Ricchii is the first, and currently the only, hermaphroditic character in Monster Musume.
 * Ricchii is implied to have a large penis, as Mosukii and Yatsume describe it as amazing, manly and strong-looking when she showed it to them.