What is yutanpo onee-san?

Yutanpo Onee-san is a popular character in Japan who is associated with keeping warm during the cold winter months. Yutanpo is a type of hot water bottle or heating pad that is used to warm up the bed or soothe sore muscles and joints. The character Yutanpo Onee-san is often depicted as a kind and caring older sister figure who takes care of her younger siblings by making sure they stay warm and cozy. She is usually portrayed wearing a warm sweater, scarf, and carrying a yutanpo. The character has been widely used in advertising campaigns for products such as hot water bottles and heating pads, and has become a beloved icon in Japanese culture.