Tenjou Yuuya, a boy who has endured bullying for years, resides with his cherished grandfather and faces relentless torment at school. Seeking respite, he takes a prolonged break from classes to mend his emotional wounds. During this hiatus, he decides to tidy his grandfather's abode and stumbles upon a mysterious room filled with souvenirs from his grandfather's global adventures. As he sifts through the items, he uncovers a hidden door camouflaged within the collection. Driven by curiosity, he swings open the door and beholds a startling sight on the other side...