While Dad and Mom are away on a local community association hot spring trip, the proactive sister Chiharu takes the opportunity to play naughty pranks on her beloved older brother. She relentlessly indulges in all sorts of mischievous activities throughout the day, from his room to the kitchen, entrance, bedroom, and bathroom, without a moment's rest. "Big brother, wow! You can make so much white stuff come out! But you can still do more, right?!"
