The plot is, as always, deceptively simple. Araragi finds himself locked in a strange classroom with Ougi Oshino, the cryptic, shadow-draped girl who has been pulling invisible strings for several arcs. To escape, he must solve the mysteries of his own past—specifically, the three “events” from his first year of high school that he never told anyone about.
If you’ve seen Bakemonogatari , Nisemonogatari , Second Season , and Tsukimonogatari ? Absolutely. You have to. Owarimonogatari