Yukina

she is a female counterpart of Yukinari, but is also the name of a Seiren female who has an allergy to men, which parallels Yukinari's allergies to females. She also had markings on her body and believed that no man would ever want her, so she concluded that nobody should ever find true love and plotted to permanently seal the link between Seiren and Earth with help from Hijiri Kanata.