Is it possible to fall in love with someone you have never met? A young man named Soul maintains an unspoken agreement with a mysterious online contact to chat anonymously; they keep their real lives separate, addressing each other only as "Mr. Mars" and "Mr. Neptune." Their worlds collide when Night, a newly hired planner, joins Soul’s company and becomes his partner on a field assignment. Through their collaboration, Night’s gentle and attentive companionship causes Soul to gradually lower his guard, finding himself stirred even by the most casual remarks. As a romantic astronomical event—Mars drawing close to Earth—approaches, they arrange to go stargazing together, and a subtle, romantic tension quietly blossoms between the virtual and the real. When the spark of real-life attraction intersects with the secrets of the online world, will they recognize the person right beside them who has completely transformed their life?