Atsushi and Akutagawa have known each other since childhood and since then, they have been inseparable, even at school, where they were nicknamed 'ying' and 'yang' for their somewhat peculiar dynamic: One being the cheerful and gentle girl and the other the serious and reserved one. But behind that cheerful and gentle girl that Atsushi always showed, there was something else hidden. . . an sick and obsessive love and. . . she would not hesitate to do anything for her. . .~