An affluent white-collar worker receives a mysterious invitation: "Would you like to know what life is about?" "Would you like to live your life fully?" It is sent into the unpredictable space of the Lord God, and future human beings will invite and challenge the present world, and the different challenges that humans face during the era of great universe development will be simulated as copies as well. The "copies" will guide the selected people to overcome many traps, meet life-and-death comrades, and become leaders. All of this is in the interest of human evolution, survival, and infinite futures!

A 2-episode OVA for Suisei no Gargantia revealed during an announcement at AnimeJapan 2014.

Third-year high school student Jirou Yakuin is in love with his childhood friend and classmate, Shiori Sakurazaka. Thus, he hopes to be paired with her for the "marriage practical": their school's practice of randomly selecting boy-girl pairs to live as pretend married couples while monitoring and rating them on how close they have gotten. Meanwhile, the lively Akari Watanabe wants to be assigned to her crush, the popular and good-looking Minami Tenjin. Much to their dismay, Jirou and Akari find out that not only have they been paired together, but so have Shiori and Minami! Determined to be with their crushes, Jirou and Akari strive to earn as many points as possible, as the top 10 pairs earn the right to switch their partners—so long as both couples agree.