The fantasy story is set in an alternate world where one can choose the form in which one is reincarnated — but choices like the "demon king" or the "hero with cheat skills in a harem" are so popular that one would have to wait in line for one to 50 thousand years. So, our protagonist chooses to be reincarnated over and over again into other bizarre forms, such as the rib of a hero with cheat skills in a harem story's happy ending, a hermit crab, or a vegetable.

[Source: Anime News Network]

Zero crash-lands on the war-torn planet Amatera with no memories and no idea who she is.
Amidst a brutal conflict between the local resistance and the imperial Gevuran forces, she meets Ring, a charismatic young leader fighting to save the world.
As Zero’s identity slowly awakens, she discovers she’s no ordinary girl—she’s a cosmic being known as Galverse, a key to something far greater than any one planet.

[Source: Shinsei Galverse on YouTube]