Reimu Hakurei, a shrine maiden from the mystical realm of Gensokyo, has devoted herself to preventing supernatural disturbances caused by the mythical creatures known as youkai. One of the traditions at her shrine is to host an annual summer celebration, where various guests from both human and youkai communities are welcomed. However, the morning of the banquet brought an unexpected development - the shrine's donation box was mysteriously gone without any trace of theft. Reimu, together with her friends Marisa Kirisame and Aya Shameimaru, took up the task of investigating the strange occurrence. As they delved deeper into the matter, they discovered that other objects had vanished as well. It gradually became clear that this wasn't a mere theft but an extraordinary event comparable to Remilia Scarlet's mist or Yuyuko Saigyouji's youkai cherry blossom.