They Were Eleven

They Were Eleven (11人いる!, Jūichinin Iru!) is a manga by Moto Hagio which ran in Shōjo Comic for three issues from September through November 1975. It was published in English as part of the anthology Four Shōjo Stories. The anime film was licensed and released in North America by Central Park Media. It was first released on subtitle VHS in the early 1990s, then later re-released on VHS in 1996 with a newly produced English Dub.

The manga was adapted as a one-episode, 40-minute television drama broadcast on 1977-01-02 as part of the Shōnen Drama Series on NHK. Ten years later, it was adapted as a theatrical anime movie, released November 1986. In 2004, a theatrical stage adaptation was produced.

Plot
Ten young space cadets are put onto a decommissioned spaceship as their final test. If they pass this test, their lifelong dreams of being valued people in their respective societies will come true. Their orders are to survive as long as they can with what they have. However, once they arrive at the ship, they find that their crew has gained an eleventh member -- and no one can remember the original lineup well enough to recognize which of them is the newcomer.

As the days pass, the eleven cadets must deal with their suspicions of each other as well as the sudden knowledge that the spaceship is in a decaying orbit around a star, which is causing the temperature on the ship to rise. With this rise in temperature, a sickness begins to spread among the crew as they work to stabilize their orbit and determine who among them is the spy.