"Telling anyone our secret will lead to your demise," warns Takatou, when he unexpectedly meets Ritsu after a mountaineering accident and spots the red birthmark beneath her right eye. Ritsu confides that a substance she ingests can turn into an elixir, piquing Takatou's interest in the mythology of the Red Leopard and prompting him to seek a deeper bond with Ritsu. Their love story unfolds against the backdrop of an ancient tale.