Kisaragi Saya, a high school girl who is so unnoticed that its practically a curse, is a loner and an introvert. During her summer break as a first-year high school student, Saya decides to pass the time by playing the MMORPG Shadow Assassins World. Even in the world of Shadow Assassins, where magical beasts and yokai run rampant, Sayas natural lack of presence stands out, allowing her to shine as Kuro, a top-tier player in the Ninja class. One day, a bright and extroverted ninja named Hikari appears, asking to become Kuro’s apprentice—what could this lead to!?