Naoko-san, a college sophomore with black hair, experiences a transformative night in Kyoto. Her evening begins at a wedding, sparking a desire to independently explore adult social experiences, particularly through alcohol. She favors cider, Bireley's, piña colada, and rum-based cocktails, and possesses extensive knowledge of alcohol production, explaining rum's origins from cane sugar and brandy's derivation from distilled wine. At a bar, she deters the inappropriate behavior of a man named Todo using a non-violent "friendly punch" technique taught by her mother. This method involves wrapping four fingers around the thumb and is intended to prevent escalation without sincere hatred. Later, she joins strangers Higuchi and Hanuki to gatecrash parties, displaying significant alcohol tolerance and participating in drinking competitions, including one against the supernatural entity Rihaku. Driven by a childhood connection to the picture book "Ratatatam," Naoko-san seeks out a used book festival. There, she assists the God of Used Book Markets in redistributing rare books collected by Rihaku, making them available at reasonable prices. Her involvement continues during a school festival guerilla theater production, though her role is interrupted when a classmate attempts to replace the male lead. Following a cold spreading among acquaintances, Naoko-san visits and nurses those affected, including the classmate who pursued her throughout the night. During this visit, he gives her the "Ratatatam" book and suggests visiting a used bookstore together, to which she agrees enthusiastically. The narrative concludes with them meeting for coffee before the bookstore visit. She is frequently identified as "the girl with black hair" or "the black-haired maiden."