Sumire Hoshino (or Perman # 3) is the deuteragonist in the series. Although Sumire is a girl, she is officially addressed as "Perman 3". However, her teammates call her "Pako". Her secret identity, which she never reveals even to her teammates, is a famous child star, who feels more free and comfortable as Pako.
(Source: Perman Wiki, Doraemon Wiki)