Episode 3

Birthmark (痣, Aza) is the third episode of Boku Dake ga Inai Machi anime.

Summary
Upon gaining the upper hand in a speed skating race against Hamada, Satoru decides to hold back from winning, which only Kenya notices, to avoid inadvertently changing the future, before recalling the exact same outcome from his past. His surreptitious forfeit angers the fellow classmate and disappoints Kayo, to whom he promised a victory.

After failing to acquire Hinazuki's birthday date, Satoru sneaks into his teacher's office and attempts to view the student file, figuring this would help him pinpoint the date of her disappearance, before being interrupted by Gaku Yashiro. Presuming the boy has romantic feeling for Kayo, Yashiro allows Satoru to view her birthday date, which turns out to be March 2nd, the same day as his. Upon his way out, Yashiro tells Satoru to give it his all and to strive towards success.

Satoru later goes to find Kayo at the park, but runs into Jun Shiratori after noticing one of his paper planes. He spends some time with him at his house, noticing how differently he views Yuuki as an adult, but is still convinced that Shiratori is not the kidnapper, due to his softhearted persona. He later learns through their dialogue that Jun met Kayo a couple of times in the park, always by herself.

Afterwards, Satoru goes to see Kayo at her house, only to find her beaten up and partially undressed in a shed. He tries to cover her with his jacket, as her mother shows up and drags her daughter back into the house. When he asks the woman as to how did her daughter get injured, Kayo replies that she fell. As the two walk away, Fujinuma is left speechless by the woman's sadistic and shameless actions. Later that evening, Kayo's mother shoves Kayo's head into the kitchen sink filled with ice water in order to hide her bruises, while Kayo's mother's boyfriend asked of her to save some ice.

The next morning, Satoru and Kayo are appointed on homeroom duty. Satoru prepares the homeroom, while Hinazuki shows up late in the middle of class. After collecting students' money for lunch, Satoru goes to his teacher's office and addressees Kayo's abusive relationship with her mother. Gaku then informs Satoru that, for the past year, child protective services have failed to prove this due to a lack of evidence.

Back in their homeroom, after Satoru reports to Gaku that the lunch money's missing, Misato accuses Kayo of stealing and suggests to search everyone's bags. Kayo later finds the money at her desk which prompts the students to call her a thief. Enraged by this, Satoru stands up for Kayo and silences the class, while Kenya suggests that anybody could have planted the money in her backpack. Yashiro gets the situation under control and reminds the students that Kayo and Satoru were appointed on homeroom duty.

Having finished cleaning, Satoru takes Kayo up a mountain to show her a frost-laden Christmas tree and suggests for them to come back in summer as well. Back at school, Kenya's seen talking to Gaku.

Characters
List of characters in order of appearance:

Anime and Manga differences

 * In the manga, a shadowy figure, later revealed to be Kayo's mother, forcefully takes her daughter home from the park.