Plot
In 1969, physically fit Taiwan native Lo Pao-tai (Ethan Juan) arrives in Kinmen as a new Republic of China Army conscript. He is selected by Sergeant Major Chang Yun-shan (Chen Jianbin) to be part of the 101st Amphibious Reconnaissance Battalion (also known as the Frogmen of the R.O.C. Army) for grueling training, where he underperforms. He helps Chang Yun-shan—an illiterate who twenty years ago was kidnapped by the R.O.C. Army from his Shandong village and forced to leave the mainland—and Chang in turn arranges for his transfer to work in the military brothel known as Unit 831.
Chung Hua-hsing (Wang Po-chieh), a friend of Lo's from back home, works in a damp tunnel and is severely bullied by other soldiers. He eventually escapes with Sasa (Lei Jiexi), a prostitute he likes, and together they try to swim to mainland China. Meanwhile, Chang feels more and more depressed and lonely, and becomes attached to Girl #8, the coquettish Jiao (Ivy Chen). Lo Pao-tai comforts him and offers to write letters for him to his mother. Lo doesn't bother to sleep with the girls since he resolves to save his virginity for his girlfriend back home, but he befriends Girl #7, Nini (Wan Qian), a mysterious but friendly Shanghainese girl who teaches him the guitar. Nini doesn't have many customers because she usually buys tickets out of pocket to meet her daily quota.
Lo accidentally discovers Nini has a son, and is in Unit 831 to work off her sentence after killing her husband. He is unhappy that Nini hasn't told him anything, so he avoids her. But just like him, Nini has also fallen in love. She decides to tell him about her past abusive marriage, and Lo forgives her. One night, she breaks the curfew and takes him to the wheat fields, where they kiss.
Already getting on in years, Chang plans to marry Jiao, get discharged, and open a restaurant in Taiwan. He begins to prepare for their wedding after receiving Jiao's consent. However, Jiao is only using him (and all her other clients) to amass a personal fortune, so she can buy her way out of the brothel. Lo tells her secret to Chang, and Chang furiously confronts her. During the ensuing quarrel, Chang strangles Jiao. Blaming himself for causing Chang to commit murder and his subsequent arrest, Lo is grief-stricken and Nini consoles him.
In 1971, Nini receives a general amnesty and is about to be transferred back to Taiwan. On their last night together, Nini is ready to make love to Lo. But Lo stops, saying he wants to save his virginity for the one he marries. Nini is hurt, but still leaves him the guitar when she departs.
A few years go by. Lo greatly misses Nini, and continues to write her letters but he has no idea where she is. He has already lost his virginity to girls he doesn't care about. Finally, he finishes his service and leaves Unit 831. Unit 831's director Chou Ching-wu (Tuo Yiran) tells him to marry and forget about the brothel.
A pre-credits scene then displays black-and-white scenes of an alternate reality: Lo is married to Nini and they have a young child, Chung and Sasa successfully made it back to the mainland, and Chang opens his dumpling restaurant in Taiwan, having married Jiao and having a baby together.
