In the far future, Earth—now known as Terra—has made contact with various other planetary civilizations. These civilizations have formulated a central school, Cosmo Academy, for the best and brightest in the universe; the entrance exam is said to be exceptionally hard, but admission to the school guarantees a position of societal influence and excessive wealth after graduation. The story follows a group of ten young space cadets on the final part of their entrance exam. The group has been ordered to board a decommissioned spaceship in orbit around a small star and survive as long as they can with what they have. They can activate an emergency beacon to signal for help, but they will most likely fail the exam by doing so.
Once the ten arrive at the decommissioned ship, they discover an eleventh member on their crew, and as the days pass, the orbit of the spaceship gradually decays, which raises the temperature of the entire ship. The eleven cadets—each from different cultures, species, and walks of life—deal with their suspicions of each other as they work to stabilize their orbit, fight off a mysterious sickness, and determine which one of them is trying to kill them all.
They Were Eleven contains the following the following tropes:
- Accent Adaptation: Frol's coarse and straightforward method o' speakin' is translated in the dub as a Dixie accent.
- Artistic License – Physics: Orbits around a single star (or other massive object) do not decay, except possibly unnoticeably slowly (as in "a few centimeters per million years", except for binary neutron stars).
- Those could be some really powerful Explosion Propulsion, Inertial Damping, and construction materials.
- Or all part of the Secret Test of Character.
- No, but the ship could be "knocked" from a round orbit to an elliptic one due to speed loss (caused by a possible leak). Although the presence of the planet should attract the ship instead, unless the ship is on the edge of the gravitational influence of the planet, well...
- Friend-or-Idol Decision: Frol catches the sickness after the students save the ship. Despite Frol's desperate pleas, everyone else agrees to activate the beacon, sacrificing the test and their own dreams to save his life.
- Human Aliens: Terrans and Sabans have very similar genetic make-up, so they both look roughly the same, even though the former are humans and the latter from another planet than Earth. It's also lampshaded in the prologue. Because of the similarities, both species have a tendency to compare themselves to eachother.
- I Lied: The Big Red Button is supposedly a full forfeit that will cause everyone to fail the exam. In reality, the exam is built around the fact that the test-takers will eventually need to press the button. The cadets are graded on how long it takes them to reach that point and how well they dealt with each crisis prior to that moment.
- Official Couple: Tada and Frol, the sequel and the short gag comic Space Street hammers this home even further by confirming that they're engaged, also King Mayan and Chuchu (the Fourth's younger sister) get married by the end of the sequel
- Royals Who Actually Do Something: King Mayan strongly comes off as this. He admits that his royal duties would not permit him to attend the space academy should they pass the test. But he wants to prove that he has the right stuff. He proves himself a capable leader and at the end, after they it's revealed that they all passed the test, and who the eleventh was, Mayan apologizes to Taba for his blunt accusations. He also feels that his experiences will make him a better King.
- Samus Is a Girl: Played with. The other students react this way the first time they see Frol out of his spacesuit, until he corrects them. When another student later sees Frol in the shower and notices that he is missing something important, most of the other students conclude that Frol is pulling a Sweet Polly Oliver until Knu makes The Reveal.
- Secret Test of Character: Besides the obvious test of ingenuity and survival skills, the exam tests how well would-be students can handle pressure with no outside support. The eleventh cadet is a supervisor who throws everything off-balance right away and continually performs acts of sabotage to pressure the team into pressing the button. Some of the things that go haywire are not part of the test, but the cadets get extra points for those.
- Space Cadet Academy: Slightly subverted. The entire ordeal that these cadets are going through is just part of the application process for admission to the academy.
- Spell My Name With An S: In the Viz translation of the manga, Tada's full name is rendered as "Tadathos" while every other translation spells it "Tadatos" instead.
- In the French translation of the manga, Frol's name is translated as "Flore".
- Ten Little Murder Victims: Subverted. While the title and the plot might make you think this would happen, ultimately, no one dies.
- Training "Accident": The vine-sickness was not part of the test. It happened only because an explosive charge that the crew needed to disable at the beginning of the test went off and knocked the ship out of orbit. The ship then got close enough to the sun for the vines to start growing again.
- "Where Are They Now?": The anime features one of these, done in the style made iconic by American Graffiti.