In the festive glow of New York's Christmas lights, Tokyo Metropolitan Police officer Akari Kido finds herself in the midst of directing traffic during her international exchange training. Amidst the holiday cheer, a witch-like figure plays a mischievous 'Christmas Party' trick, leading to a perilous moment as a runaway trailer truck hurtles towards Akari. In the nick of time, a enigmatic girl materializes, declaring her mission to safeguard both New York and Akari from harm.