Mari Tamaki has always dreamed of what lies beyond the boundaries of the cosmos, filled with an overpowering feeling of curiosity for the world around her. Despite having such lofty goals on the inside, her fear of the unknown and concern about her own potential limits have always kept her from pursuing them. Mari, now in her second year of high school, is more determined than ever to not waste any more of her youth. Still, her anxiety prevents her from taking that bold step forward—that is, until she has a fortuitous meeting with a girl who has big goals of her own.