context: Air Japan flight JA307 is enroute from Tokyo's Haneda airport south
  to Itami Airport in Osaka. As stewardess Kuzumi Asakura [Tomomi Sato] announces the
  flight plan, which will take them over the island of Oshima and the city
  of Suzuka, the pilot notices an unusual blood red color to the sky around
  them. That's when the trouble starts.One by one, the passengers begin seeing bloody birds flapping their
  wings against the windows as though in fear. The pilot [Hiroyuki Nishimoto] receives a radio
  message to the fact that there may be a bomb aboard and is ordered to
  return immediately to Haneda. Co-pilot Sugisaka [Teruo Yoshida] is ordered to check the
  bags of each of the passengers, giving the excuse that a bag containing
  confidential documents may have mistakenly been loaded on this flight. All
  bags are clean and only one man [Hideo Ko] has no bag, but Kuzumi notices an
  unaccompanied suitcase under a bench. Sugisaka opens it and finds not a
  bomb but a rifle. The man without a suitcase suddenly pulls a gun on
  Sugisaka and then orders the pilot to change course to Okinawa. To show
  that he means business, he fires through the cabin a shot that knocks over
  a transistor radio breaking the news that a UFO has just been spotted over
  Japan and that Japanese and US Air Force fighters are in pursuit. Suddenly
  a large luminous object is spotted directly in front of the airplane. It
  passes overhead but knocks out the airplane's gauges, sparking a fire in
  the engines. Air Japan flight JA307 goes down on what looks like an
  uncharted desert isle.Sugisaka is the first to awaken but the pilot is dead as well as the
  hijacker. Kuzumi is next to recover. Together, Sugisaka and Kuzumi check
  for more survivors. There is Mrs Neal [Kathy Horan], an American Vietnam War widow;
  Senator Mano [ Eizo Kitamura] of the Constitutional Democratic Party; weapons exporter Tokiyasu [Nobuo Kaneko] and his wife Noriko [Yuko Kusunoki], who flies into Mr Mano's arms when she finds
  that she has survived the crash; Psychiatrist Momotake [Kazuo Kato]; space biologist
  Professor Sagai [Masaya Takhashi]; and the young man who called in the bomb threat (whom
  they lock in the cockpit). Taking stock of the airplane, they find that
  they are out of water, have no food nor any idea of where they are. What's
  worse is that a radio announcement says that a search has not uncovered
  any trace of the downed airplane, so the search has been discontined.As Sugisaka worries about surviving, and Mano worries about his
  upcoming election, and Tokiyasu worries about himself, and Sagai offers
  scifi explanations, and Dr Momotake studies survival instincts clashing
  with egos, the hijacker suddenly revives, grabs Kuzumi as a hostage, and
  runs out into the night where they come upon a luminous spaceship. Kuzumi
  crouches behind a rock, but the hijacker steps into a clearing to get a
  better look. Suddenly, his face goes blank and he begins walking toward
  the spaceship. A dark blob crawls along the ground towards the hijacker.
  When she sees the hijacker's forehead split open from nose to hairline,
  Kuzumi screams and passes out.Sugisaka finds Kizumi passed out behind the rock and carries her back
  to the airplane. In order to get Kuzumi to tell what she saw, Dr Momotake
  hypnotizes her. Kuzumi tells how the dark blob crawled into the hijacker's
  skull through the split in his forehead. Tokiyasu doesn't believe her, but
  Dr Momotake assures him that Kuzumi is telling the truth. Sagai points out
  that it could be a flying saucer and backs up his suspicion with the fact
  that reports of UFOs have increased ever since the bombing of Hiroshima,
  giving extraterrestrials ample opportunity to invade the Earth while we
  are preoccupied with senseless wars. While everyone bemoans the horrors of
  war, the kid who called in the fake bomb threat goes berserk, not wanting
  to believe Kuzumi's story. He attacks Dr Momotake, who falls off the
  cliff. Waiting at the bottom is the hijacker. He latches on to Momotake,
  bites his neck, and sucks out all his blood, turning Momotake a bright
  shade of blue.A few hours pass as the survivors discuss the need to find water in
  the morning. Suddenly, there comes a knock on the door. Mano and Tokiyasu
  don't want to open it, but Sugisaka does anyway. As he descends the
  stairs, he sees the hijacker lying on the ground and notices the big scar
  on his forehead. Mrs Neal, whose husband was killed by a napalm blast to
  the face, rushes to the hijacker and begs for the others to help him.
  Against their better judgement, they carry the hijacker inside and dress
  his wound.Mano is becoming extremely thirsty, thanks to the bottle of whiskey
  that Tokiyasu gave him. Now, when Mano wants a drink of water from
  Tokiyasu's canteen, Tokiyasu refuses. It seems that Mano and Tokiyasu have
  been greasing each others' palms, Tokiyasu funding Mano's campaign and
  Mano promising to pressure the committee to accept Tokiyasu's weapons bid,
  a promise that Tokiyasu had no intention of keeping. In revenge, Tokiyasu
  picks up a rifle and forces everyone out into the night then locks himself
  in the safety of the airplane. But he forgot one person...the hijacker.Tokiyasu's screams can be heard outside the airplane. Suddenly, the
  screams stop and the locked door swings open. Everyone rushes inside to
  find Tokiyasu dead on the floor, all the blood drained from his body.
  Noriko begins to laugh, exclaiming that she is now free from here
  husband's abuse, but her laughter soon turns to tears when she thinks
  about the way he died. When no one is looking, the hijacker comes out of
  hiding and carries Noriko off to the spaceship. When the others notice
  that Noriko is missing, they go in search of her.The sun is rising, and Noriko can be seen standing on a ridge. She
  raises her hand to speak, but it is not her voice. It is the Gokemidoro
  speaking through her. They have come to invade the earth, says the voice,
  and to exterminate the human race. That said, the Gokemidoro have no more
  need for Noriko's body, so she plunges off the cliff. By the time her
  fellow passengers get to her broken body, she has disintegrated into a
  shriveled old cadaver.Once again, the passengers get into an argument about whether or not
  there are such things as extraterrestrials who would evade the earth.
  Professor Sagai theorizes that the Gokemidoro have taken over the
  hijacker's body and turned him into a vampire. Mano thinks that is
  balderdash and challenges them to show him a vampire. Sagai agrees that he
  would like to see one, too. The only way to do that is to sacrifice one of
  them to the Goke. But who will it be? Mano suggests Mrs Neal, because a
  foreigner will be less problems later. Mrs Neal screams that she doesn't
  want to die. Sugisaka is against the entire idea. A knocking on the
  cockpit door and a cry for water remind them of the kid who made the bomb
  threat, so they let him out. Mrs Neal grabs a rifle and locks Sugisaka and
  Kuzumi into the cockpit. Mano and Saiga shove the kid outside. Then they
  line up in the windows to watch the hijacker slowly advance. The kid pulls
  out the bomb he's been hiding and vows to blow up the plane unless they
  let him back in. They don't, the hijacker continues to advance, and the
  bomb goes off, killing the kid and blowing a large opening in the side of
  the airplane.It's now evident that the plane can no longer provide cover, so
  they'll have to get moving. But the bomb blast has wounded Professor
  Sagai. Mano could care less and runs off. Mrs Neal follows him. When the
  hijacker catches up with them, Mano pushes Mrs Neal towards the hijacker
  in order to save himself. Mrs Neal shoots at the hijacker a number of
  times but keeps missing. Finally, the hijacker grabs her, fastens his lips
  to her neck, and sucks her dry.Back in the airplane, Sugisaka and Kuzumi are packing up supplies
  while Sagai bemoans his loss of faith in humanity. As Sugisaka assures him
  that they must believe in human goodness, they hear a shout outside. It is
  Mano, and the hijacker is not far behind him. Sugisaka and Kuzumi go out
  to help Mano, but he quickly runs inside the plane, locking the door
  behind him. The hijacker turns on Sugisaka and Kuzumi. While Mano watches
  from inside the plane, Sugisaka tosses a bucket of airplane fuel at the
  hijacker, then sets him on fire.The Gokemidoro crawls out of the burning hijacker, creeps into the
  airplane through the bomb hole, and makes its way into Professor Saiga's
  forehead. Saiga drinks his fill on Mano, then turns to Sugisaka and
  Kuzumi, who try to run. Saiga follows until they are stopped by a
  landslide that knocks Saiga from the hill they are climbing. Sugisaka and
  Kuzumi keep running, while Saiga makes his way back to the spaceship. Once
  Saiga is there, the Gokemidoro crawls out of his skull, reducing Saiga to
  a pile of dust.Sugisaka and Kuzumi keep running until they come out on a highway
  where they see cars lined up at a tollbooth. Everyone in the cars is dead.
  Everyone in the city is dead, too. The voice of the Gokemidoro can be
  heard, giving the same message it spoke through Noriko...that they have
  come to invade the earth and to exterminate the human race. Cut to footage
  of mushroom clouds.Epilogue: Sugisaka and Kuzumi are wandering on rocky terrain. Sugisaka
  wonders why this had to happen. Pan from the earth to outerspace where a
  whole fleet of Gokemidoro spaceships are headed towards us. [Original Synopsis by bj_kuehl.]
question: Who has invaded Earth?
answer: Aliens