In the spring of 1998, 15-year-old Kouichi Sakakibara has just moved to the town of Yomiyama, where he is set to attend the local middle school Yomiyama North. However, when a past injury resurfaces, he is placed in hospital, leading him to miss the first week of school. Though he recovers quickly, before leaving he meets Mei Misaki, a strange, eye-patched girl whose cryptic mannerisms spark a subtle interest within the boy.

At Yomiyama North, Kouichi is placed in Class 3-3. However, beneath the innocent atmosphere, he finds the class' behavior odd: everyone seems to be on edge and watchful of Kouichi's actions. Moreover, Mei is a student in the class, yet both classmates and teachers do not show any regard for her, as if she is simply not there. Though more oddities arise and more questions spring forth, no one is willing to give Kouichi any answers. With little choice but to ease his growing curiosity, Kouichi starts to pursue Mei for help, against both the class' and her own warnings.

Another was originally serialized in Kadokawa Shoten's literary magazine Yasei Jidai (野性時代) intermittently from the July 2006 issue to the May 2009 issue. It was published as a 677-page hardcover novel on October 29, 2009. It was later published in two-volume format and again under Kadokawa's Sneaker Bunko label with illustrations by Noizi Itou. The original cover art was created by Enta Shiho (遠田志帆).

The novel ranked third in the 2010 Kono Mystery ga Sugoi! and the 2010 Honkaku Mystery Award.

Another was published digitally in English by Yen Press under the Yen On imprint on March 19, 2013. The publisher released the series in print as a hardcover omnibus on October 28, 2014. It was also published in Brazilian Portuguese by Editora JBC in 2015.