2화: 세르게이 크라이네프와 유키나의 오빠 실종 사건 수사
Sakurai requests the group to investigate a Jewish Russian violinist named Sergei Krainev, who the Kwantung Army suspects is a foreign spy who has been leaking out classified military information to an unknown benefactor. Yukina is told privately by Sakurai that her older brother Isao Takachiho had disappeared to Manchuria after the death of her father. Aoi and Yukina sees no reason as to why or how Krainev could be a spy, after having met with him personally. While Krainev begins his performance at the town hall, Aoi and Yukina realize that the fast section of his piece is a coded message that will be broadcast by radio. Even though they cut off the power supply of the town hall in time, Krainev continues to play for the love of his music. (Source: Wikipedia)