Theirs is a world of three sexes: man, woman, and one more, a third sex. Kizuna, a third, is unable to process her friend's suicide. She starts dating the "woman" Shino and "man" Tougo. But each of the three has different expectations, and their relationship grows distorted... The "woman" Shino who holds darkness in her heart even as she hungers for love. The "man" Tougo who is captured by carnal desires. The "third" Kizuna whose own feelings and sex are ambiguous. Within this risky love triangle, Kizuna impossibly becomes pregnant.