Mangan is one of several neighboring boys whom the narrator plays with after school. Mangan never speaks in the story and is mainly notable for having an older sister.

Mangan's sister habitually calls him in when it is time for tea. When his sister would stand outside and wait for Mangan to appear, the whole group of boys would walk up the street with him to see him into his house. The narrator tells us that Mangan would always "tease" his sister before coming in. This delaying tactic gives the narrator the opportunity to watch and listen to Mangan's sister more than he would have otherwise.

As a result of this contact, the narrator comes to fancy Mangan's sister. Going to an all-boys school, the narrator probably has relatively little contact with girls. His observations show that he finds Mangan's sister attractive:

Her dress swung as she moved her body, and the soft rope of her hair tossed from side to side.

Because she lives across the alley, the narrator can also watch through the blinds to see when she leaves for school and thereby time his own departure so that he can follow her. This proximity allows him to increasingly imagine her as an idealized figure.