Rainbow Days follows four high school friends—Natsuki, Tomoya, Keiichi, and Tsuyoshi—as they navigate love, friendship, and everyday teenage life. Each has a distinct personality and romantic interest, but their bond stays strong through laughs, misunderstandings, and heartfelt moments. Readers enjoy the lighthearted comedy, relatable character dynamics, and the cozy, upbeat feel of watching these friends support each other while chasing their crushes.