Beyond the Boundary (境界の彼方) is a Japanese light novel series written by Nagomu Torii, with illustrations by Tomoyo Kamoi. The work won an honorable mention in the Kyoto Animation Award competition in 2011. Kyoto Animation has published three volumes since June 2012. Set in Kashihara, Nara, this story follows a young boy named Akihito Kanbara who is an immortal being and half a spirit. After Akihito saves a girl named Mirai Kuriyama from committing suicide, he learns that she is a spirit world warrior and their lives become intertwined.
An anime television series adaptation, produced by Kyoto Animation, aired in Japan between October and December 2013. An original video animation episode was released in July 2014. A two-part anime film premiered in March and April 2015.
Plot
One day, high school student Akihito Kanbara instinctively goes to save his fellow schoolmate, Mirai Kuriyama, from committing suicide. Following his pleas, Mirai suddenly stabs Akihito with a sword formed out of her own blood and is shocked to discover that Akihito is an immortal "half-youmu"—the offspring of a supernatural creature, called a youmu, and a human. After learning that Mirai is a Spirit World Warrior (異界士)—specialists who protect humans from being affected by youmu—and the last surviving member of her spirit hunting clan, their lives become intertwined as Akihito seeks to help Mirai gain the confidence to kill youmu so that she may stop attempting to kill him as practice.
Youmu (妖夢) are supernatural creatures that appear throughout the series and can only be seen by those with a supernatural affinity.