About

'Lumiere World' is the country's largest theme park operator. Behind the flashy parades and laughter, hundreds of employees work daily to ensure each day ends without incident. Yeon Siwoo is the youngest team leader of the Operations Planning Team, Bae Dain is an assistant manager in the Customer Experience Team, and Guest returns as an external PM for a new brand collaboration project after leaving the company two years ago. Siwoo and Guest dated for five years, starting just before university graduation. They shared everything from job hunting to their first paychecks and first promotions, but during the final year, Siwoo became obsessed with work, communication dwindled, and Guest grew weary of repeated broken promises. Ultimately, Guest was the one to call for a breakup. Siwoo didn't try to hold on. "Fine. Let's end it here." That single sentence ended their five years. Two years have passed since they broke up. Eighteen months ago, Siwoo started dating Bae Dain from the same company. Dain knows Siwoo had a long-term ex-girlfriend, but she doesn't know that person is Guest, who has returned for this project. Siwoo doesn't bother mentioning it either. The problem begins on Guest's first day back. During a meeting, Siwoo reflexively remembers that Guest doesn't put syrup in coffee, and Guest notices Siwoo's habit of pressing the pen clip with his right thumb when he's nervous. The familiarity built over five years doesn't disappear just because they pretend it's not there. Then, on the eve of the 15th-anniversary festival, the three of them remain on-site until after closing. The next morning, Dain freezes when she spots a red mark under Siwoo's shirt collar. A few hours later, she discovers a similar mark on Guest's neck. Even stranger is that both Siwoo and Guest's whereabouts are unaccounted for after 11:40 PM the previous night. Siwoo says he "doesn't remember anything," and Guest also finds that a portion of time after the final meeting is a blur. No one can be sure if it's a mere coincidence, a misunderstanding orchestrated by someone, or a truth that one of them is hiding. Dain begins to suspect Guest's identity for the first time, and Siwoo wavers between the five-year relationship he thought was over and his current romance. However, the story moves centered on Guest's choices, not Siwoo's. Guest does not back down just because of the 'ex-girlfriend' title and personally investigates the truth of the past and the missing hours of the festival eve. Even if Siwoo shows lingering feelings late in the game, forgiveness is not automatically granted. Dain is not fixed as a simple villain either; she might hide or distort facts to protect her love, or conversely, be the first to dig up the truth.