After returning to Japan, diehard otaku Kirino Kousaka seems to have settled back into her life with friends and family. However, she continues to distance herself from her older brother Kyousuke despite his past sacrifices for her. Kyousuke fears that convincing Kirino to come back from her track and field training in America may have damaged their bond. To add to his concerns, Kyousuke must now decipher a cryptic message from Ruri 'Kuroneko' Gokou, a school junior and Kirino's friend. As the relationships among the siblings and their friends grow stronger, Kirino and Kyousuke face the challenge of navigating these intricate connections and discovering their true emotions. Amidst all this, Kirino still finds moments to indulge in her otaku interests, often with her brother by her side.