Plot
Rita Vrataski is a young soldier in the United Defense Force (UDF), a military unit which has been sent to approach and study Darol, an enormous extraterrestrial plant which landed on Earth one year prior and been dormant since then. On the aliens one year anniversary on earth, Darol suddenly sprouts monstrous vegetation which attacks the UDF soldiers. Rita is killed, but awakens again on the morning of that day, finding herself trapped in a time loop.
After being killed twice more by the alien vegetation, Rita attempts to escape the time loop both by deserting the UDF and committing suicide by drowning, to no avail. She resolves to fight Darol, despite feeling isolated as no one else is experiencing the time loop's effects and do not believe her if she attempts to tell them. Through numerous loops, Rita improves her combat aptitude against the aliens, but twice experiences a reset of the loop despite not having died.
She soon discovers Keiji Kiriya, another UDF soldier, who is also experiencing the time loop and has been secretly watching her efforts to break free. The two surmise that they are both stuck in the loop, and that it resets if either of them should die, because they were both present when a specific class of the aliens with the ability to manipulate time was killed before Rita died. They assume that if they kill that same alien once more, the time loop may break.
Rita and Keiji eventually succeed in killing that alien again, but find that the time loop simply resets as normal with no apparent changes. As a last resort, they make contact with Shasta Ray, a UDF scientist, who tells them that Darol is seeking to wipe out the human race and is assimilating the both of them into itself through the time loop. It is surmised that they will only have one or two further chances to break from the loop before they are completely assimilated.
Rita and Keiji climb Darol in order to strike its core and defeat it. Keiji realizes that he is being subsumed into Darol first, and fights with Rita, insisting that he must be sacrificed in order to defeat it. Rita refuses, as she wishes for both of them to survive. Ultimately, she kills Darol, causing the loop to break and return to the previous morning, where Darol is found to have died, with no one except Rita remembering the cause of its death.
Rita assumes that Keiji died when he was assimilated into Darol, and is at first distraught. However, Keiji is revealed to have survived, although he does not remember the time loop nor his experiences with Rita. Rita tearfully reunites with Keiji.
