"Yankee-kun to Nemuru Onee-san" is a Japanese manga series written and illustrated by Kawaguchi Kaiji. The story follows a high school delinquent known as Yankee-kun, who is tough and rebellious, and his interactions with Nemuru Onee-san, a laid-back and mature woman who works at a nearby convenience store. The series explores themes of friendship, personal growth, and the contrast between youth and adulthood. Through their unique relationship, both characters learn valuable life lessons while navigating the challenges of their respective lives. The manga combines humor and heartwarming moments, making it relatable to a wide audience.