"Star-Crossed!!" is a manga series that blends elements of romance, comedy, and supernatural intrigue. The narrative centers around Hoshina Yuzuru, a high school student who harbors a deep fascination with the stars and astronomy. His life takes an unexpected turn when he encounters a mysterious girl named Tsukishiro Aya, who claims to be a princess from the moon. Aya explains that she has come to Earth to escape an arranged marriage to a prince from the sun, a union intended to bring peace between their warring celestial kingdoms. However, her presence on Earth disrupts the balance between the sun and moon, leading to escalating tensions and supernatural consequences.

As Yuzuru becomes entangled in Aya's plight, he discovers that he possesses a unique ability to stabilize the chaotic energies caused by the imbalance between the sun and moon. This ability draws the attention of both celestial factions, who see Yuzuru as a key to resolving their conflict. The sun kingdom sends its own emissaries, including the determined and fiery prince Kakeru, to retrieve Aya and force her into the arranged marriage. Meanwhile, Aya's loyal moon guardian, Luna, works to protect her princess while grappling with her own feelings of duty and loyalty.

The story explores themes of love, destiny, and the struggle against predetermined roles. Yuzuru and Aya's relationship evolves as they navigate the challenges posed by their respective worlds, with Yuzuru often questioning whether their connection is genuine or merely a result of cosmic forces. The series balances lighthearted moments of humor with dramatic confrontations, as the characters confront their fears, desires, and the weight of their responsibilities. The interplay between the sun and moon kingdoms serves as a backdrop for the characters' personal growth, highlighting the tension between individual choice and the demands of tradition.