Returner (2002)

Plot
Milly is a female soldier from the year 2084, when the human race is on the verge of extinction at the hands of an alien race, the Daggra (which means "enemy" in Tibetan). At the human resistance's final stronghold in Tibet where they are under heavy attack by the robot like Daggra who have force fields that guns cannot penetrate, as all her friends are killed, Milly rushes to the newly built time portal and leaps into it, just ahead of a flying bomb. It sends her to October 19, 2002. Her mission is to kill the first Daggra who faked a crash landing and stop him signaling the others and so stop the war which starts on the morning of October 22.

Milly lands in the aftermath of a shootout where a hit-man named Miyamoto finally has the murderous Mizoguchi at gun point. Her arrival allows him to escape and Miyamoto takes Milly who he believes he has accidentally shot, back to his place. She has been saved by a plate of metal in her coat and with the threat of a tiny bomb taped to his neck, she persuades Miyamoto to aid her in her mission to prevent the war in her timeline from occurring. Miyamoto also has a personal score to settle with crime lord Mizoguchi , who killed his childhood friend by kidnapping him with other children and having him cut up for his organs. Mizoguchi now belongs to a very powerful Chinese Triad.

With the help of Shi who is a mine of information as well as a seller of guns, they track down the crashed spaceship but it has already been taken away by the military to the National Institute for Space Science. The couple try to get to the captured space ship to kill the alien, and confront it as Mizoguchi arrives with his armed men to take the establishment over. Milly looks at the alien and it is not what she expected. She hesitates to kill it as bullets fly and people die as Mizoguchi advances on the lab.

The alien communicates that it wants to go home, using Miyamoto as its mouthpiece and she begins to realise that she has been told a lie. The humans, not the aliens started the war which exterminated the human race. They did it by capturing and killing this alien. She realises that they have to stop Mizoguchi killing the alien as he wants the alien technology to take over Japan and maybe the world. Milly uses her time bracelet to escape the lab, which allows her to move fast enough to dodge bullets and not be seen and Miyamoto barely gets away as the lab is blown up after the space ship has been stolen by the bad guys.

The final confrontation is on a platform at sea where they kidnap the dying alien but are battled by Mizoguchi and his men every step of the way as they try to get to the heli-pad on the roof. They make it but seem to be too late as it is now sunrise, the alien is dying, almost dead, and the Daggra space ships which have been contacted by the alien, leave the mother ship and descend to Earth. Miyamoto lets off a large bomb which takes out the henchmen but when the explosion is over, they find Mizoguchi still hanging onto life and pointing a gun at them.

He fires and his bullets bounce off an invisible force field before hitting Miyamoto but Mizoguchi has no such force field and a bullet through the head finally kills him. A minute later an alien craft arrives, disguised as an airplane and the robot like Daggra turned out to be the same as the captured alien, but wearing protective suits of armour. They revive the dying alien and restore him to health.

The aliens leave and as the war has never happened, Milly starts to fade away, going back to the future. Miyamoto decides to give up his life of violence and hands in his guns to Shi. Shortly afterwards, he is confronted by a henchman whose life he had spared earlier and a bullet is fired at his heart. He apparently dies as the henchman escapes. Long seconds pass and then Miyamoto staggers up and finds his life was saved by a plate of metal the same as that which saved Milly. She had known he was due to die and had come back into the past again, putting the plate of metal (with a message written on it) in his coat in the place where she knew the bullet would strike before going back to the future again.
in my opinion this is a good science fiction film

i agree this is a good plot and intersting ending

It's good for 2 reasons
1. it has aliens
2. it has timetravle