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Watch Senkou no naitoreido online — it may be available on legal streaming platforms such as YouTube, Netflix, Prime Video, Hulu, Disney+, and others.

The story is set in Shanghai in 1931, when the Imperial Japanese Army has been dispatched to mainland China due to the relatively recent First Sino-Japanese War, Russo-Japanese War, and World War I. In this cosmopolitan city of intrigue, there is a special military spy organization called "Sakurai Kikan" that has since been buried in history.