Nijiiro Days chronicles the daily escapades of four high school boys: the romantic Natsuki Hashiba, the tough Keiichi Katakura, the smooth Tomoya Matsunaga, and the clever otaku Tsuyoshi Naoe. Balancing academic struggles with mischief and love pursuits, these friends navigate their teenage existence. When Natsuki faces a heartbreak on Christmas Eve, a chance encounter with a girl in a Santa Claus outfit changes his outlook. This mysterious girl, Anna Kobayakawa, turns out to be a fellow student at his school. Determined to win Anna's heart, Natsuki braves the obstacles posed by his meddling friends in his pursuit of love.