Poco's Sister

Poco's Sister is an unnamed tertiary ally featured in the first part of JoJo's Bizarre Adventure, Phantom Blood.

As the older sister of Poco, she encourages her younger brother to grow stronger and stand up for himself. After being kidnapped by Dio Brando, she courageously declines the vampire's offer to join him. Instead, she joins the group once Jonathan Joestar protects her from the monstrous Doobie.

(Source: JoJo's Bizarre Encyclopedia)