OWARIMONOGATARI: End Tale Part 1

Before we witness the series’ climactic showdown in the third volume of the End Tale-each part of which forms its own cohesive whole-narrator Araragi wrestles with a crucial bit of history that had turned him into the loner we met at the very beginning, who opined that friendships only lowered his intensity as a human.
What initiates his pilgrim’s progress of a reckoning is his first encounter, at school, with the mysterious freshman Ogi Oshino, self-described niece of the equally enigmatic aberration expert Mèmè, and the book’s opening chapter is a harrowing standalone novella of a whodunit involving a locked room of sorts.