Fūko Hoshikawa is the elder sister of Kouta Hoshikawa, the main human protagonist of the series. As a member of the Hoshikawa family, she is characterized as a quick, lively, and highly active girl. Her personality includes a somewhat self-centered and shallow side, but this is balanced by a genuine care for her friends and family, even if she does not always openly express it. Fūko often engages in spirited fights or arguments with her younger brother, yet she demonstrates her underlying concern for him by offering help when he encounters difficulties. Her role in the story is primarily defined by her relationship within the Hoshikawa household and her interactions with her brother and his allies.