Mahiru Shiina, known as the "Angel" for her exceptional qualities, lives a separate life from her next-door neighbor Amane Fujimiya. Despite being neighbors, they've never had a conversation until Fujimiya spots Shiina sitting on a swing during a rainstorm and lends his umbrella. Shiina returns the favor by nursing Fujimiya back to health after he catches a cold, but her actions eventually lead to a deeper involvement in his daily life, including cooking and cleaning for him. Their initial interactions gradually develop into a unique relationship.