Koda Mari is a green-haired police officer in the International Investigation Unit of the Higashi-Shinjuku Police Department. Energetic and cheerful, she's dedicated to helping anyone in need, regardless of nationality. Arikino Ryo is a Chinese interpreter at the Tokyo Metropolitan Police Department's Interpretation Center. He has committed himself to providing precise translations between officers, witnesses, and suspects. However, he decides to leave the police force after a painful incident. When Mari and Ryo cross paths, they join forces to solve all sorts of multinational cases. As they interact with foreign residents and share meals from around the world, Mari and Ryo's journey sheds light on the challenges and experiences of living in a foreign land.