The third season of Tate no Yuusha no Nariagari. After defeating the Spirit Tortoise, Naofumi has no time for rest. An attack from the next Guardian Beast is imminent, but the three other Cardinal Heroes have gone missing. So, Naofumi and his party set out to search for the legendary trio.

Among all the beasts that roam the world, there are unique types of "ultimate species" that harbor immense strength and magical prowess considered to be at the top of the power scale. As such, many humans covet their abilities, leading some of these species to the brink of extinction. As a beast tamer, Rein Shroud can employ the assistance of various animals for many tasks, such as reconnaissance and logistics. By virtue of his ability, he joins a party led by the vile and manipulative hero Arios Orlando, only to be banished after six months due to his uselessness as a non-combative class. However, unbeknownst to the team that cast him away, Rein is an exception among beast tamers. His potential becomes apparent when he meets Kanade—a cat spirit who is also one of the ultimate species—and is able to form a contract with her. With Kanade by his side, Rein sets out on his journey as an adventurer, steadily rising up the ranks and meeting more ultimate species along the way.

In 1972, a popular student in Yomiyama North Middle School's class 3-3 named Misaki passed away during the school year. Since then, the town of Yomiyama has been shrouded by a fearful atmosphere, from the dark secrets hidden deep within. Twenty-six years later, 15-year-old Kouichi Sakakibara transfers into class 3-3 of Yomiyama North and soon after discovers that a strange, gloomy mood seems to hang over all the students. He also finds himself drawn to the mysterious, eyepatch-wearing student Mei Misaki; however, the rest of the class and the teachers seem to treat her like she doesn't exist. Paying no heed to warnings from everyone including Mei herself, Kouichi begins to get closer not only to her, but also to the truth behind the gruesome phenomenon plaguing class 3-3 of Yomiyama North. Another follows Kouichi, Mei, and their classmates as they are pulled into the enigma surrounding a series of inevitable, tragic events—but unraveling the horror of Yomiyama may just cost them the ultimate price. [Written by MAL Rewrite]

TV version of including an entirely new first episode. The first episode depicts Rengoku as he embarks on his journey to the Mugen Train. The remaining episodes will add about 70 new animation cuts and new background music, as well as a new trailer. (Source: ANN)