The Last Mission follows Dan, a mischievous and optimistic angel who is tasked with a final mission to return to heaven: he must find true love for Lee Yeon-seo, a talented but cold-hearted and cynical ballerina who lost her sight and her dreams after a tragic accident. Yeon-seo, having inherited a massive fortune, is surrounded by greedy relatives and has lost her faith in humanity, making Dan's task nearly impossible. As Dan intervenes in Yeon-seo's life, he finds himself falling in love with her, complicating his divine mission and risking his existence. The series explores themes of redemption, sacrifice, and the healing power of love, as the two navigate personal trauma, corporate conspiracies within the ballet company, and the supernatural rules governing Dan's celestial nature.