Owarimonogatari

Koyomi finds himself trapped in a phantom classroom with Oshino Ougi, apparently stuck there with time frozen due to the effects of another Oddity. Ougi determines that they are trapped there because of a similar incident that happened two years ago, when Koyomi was a high school freshman, and marked a turning point in his life. He recounts the incident, which involved an alleged leakage of the answers to a maths exam during a study session, and how a classmate of his, Oikura Sodachi, was determined to find the culprit. Among the suspects are those who scored highest, which included Koyomi and Sodachi themselves, and the argument is heated until the matter is put to a vote, and Sodachi is herself chosen as the culprit. She never came to school again since. Koyomi however, personally believed that it was their maths and homeroom teacher Tetsujou Komichi who was responsible, adjusting enough of the questions in her own exam to match the study session. That she herself voted for Sodachi made him lose faith in people and made him ever more withdrawn and cynical since. This allows Koyomi to leave the classroom. The next day, Koyomi comes to class, and is warned by Hanekawa not to enter the classroom, as Sodachi has suddenly returned to school.

Koyomi enters the classroom against Hanekawa's advice and talks to Sodachi, who has a venomous hatred for him, and he cannot believe that it comes simply from the class meeting two years ago, as she enigmatically mentions that he has no idea what makes him what he is, as he cannot remember what was in his shoe locker the first year of middle school. She winds up stabbing him in the hand with a pencil just as Hitagi comes in, although Hanekawa is tying to stop her, and the two have a fight. Later, Ougi accompanies him to his former middle school, and they go to his old shoe locker, which contains envelopes with his name on them. One of the envelopes contains a map, which leads to a dilapidated old house where Koyomi remembers that he explored regularly every summer during middle school, and where he met a girl.

Koyomi recounts to Ougi how he had originally found similar letters in his shoe locker when he was in his first year of middle school, and how they intrigued him. He came to the house and the girl explained how she had sent similar letters to others and how he was the only one who responded. She began helping him study maths and this helped him to become as good at it as he eventually became, and was critical to him getting into Naoetsu High School three years later. She imposed three conditions on him that they should always meet only in the house, to keep the study sessions a secret, and that he should not probe into her life. On the last day of summer vacation Koyomi went to the house as before and found it empty. He found an empty envelope taped to the bottom of their study table. He never saw the girl again. He tried looking for her at school to no avail. Ougi concludes that the mystery girl must be Sodachi, although he is perplexed at why she would not have reminded him of their former acquaintance when they later became classmates in high school. Ougi explains that the reason why Sodachi invited him over for their study sessions was because her family was experiencing domestic violence and that she knew that Koyomi's parents were police officers, and she hoped he and his parents might be able to help her family. His middle school self, however, was not able to understand this and her family eventually fell apart completely by the end of that summer. The next day he shares Ougi's conclusions with Hanekawa, who points out Ougi's conclusion hinges Sodachi knowing that Koyomi's parents were police officers, a fact which Koyomi generally keeps secret to avoid problems. He realises that his relationship with Sodachi must go further yet and there is more he still needs to remember.

Hanekawa reveals her concerns about Ougi as she and Araragi go to visit Oikura. Source: crunchyroll

Araragi and Hanekawa visit Oikura and learn the painful story of her family's past. Source: crunchyroll

Ougi claims to have figured out the whereabouts of Oikura’s mother and, in her own way, helps Araragi and Hanekawa to solve the mystery. Source: crunchyroll

Koyomi Araragi waits in the ruins of the cram school to ask Suruga Kanbaru for help, a request he hopes she will refuse. Source: crunchyroll

After a hurried departure from the cram school ruins, Koyomi and Suruga head toward the meeting place, only to encounter some difficulty along the way. Source: crunchyroll

Having finally arrived at the meeting place, Koyomi and Suruga find an unexpected person waiting for them. Before their reunion can take place, they must face an unexpected foe! Source: crunchyroll

The group relocate to the North Shirahebi Shrine where Izuko Gaen tells them the story behind the location and the effect Shinobu’s first minion had on it. Source: crunchyroll

Koyomi is confronted by Shinobu’s first minion, the original apparition killer. But instead of starting a battle, the samurai makes a simple request. Source: crunchyroll

As Koyomi prepares for his duel, he learns of the crisis that Hanekawa is facing and must decide what battle he should fight. Source: crunchyroll