Doraemon: Nobita and the Knights on Dinosaurs

Nobita argues that dinosaurs still exist. Suneo quickly disproves him, while Gian and Shizuka take Nobita's side and insist dinosaurs could still be around. The disagreement sets off Nobita's search for proof with Doraemon's help.

Nobita asks if there are any dinosaurs still alive on Earth. Doraemon uses a gadget to show that dinosaurs are extinct, which dampens Nobita's curiosity. The moment shifts the group's attention from belief to a quest for other explanations.

Nobita struggles to keep his test papers hidden from his mom, fearing punishment for neglecting studies. He looks for a secure place to stash them as distractions mount around him. The drive to hide them pushes him toward Doraemon's extraordinary options.

Gian loses control of Suneo's remote-controlled airplane, and it crashes into the river. Suneo spots a huge dinosaur in the water, which frightens him and makes him flee. The sighting marks the first extraordinary phenomenon beneath their town.

Nobita and Doraemon reach the hill behind their school, where Doraemon uses the Anywhere Hole to reveal a hidden tunnel. They descend into darkness, entering an unknown underground world. The discovery raises questions about what else might lie beneath their town.

That night, Suneo spots the same dinosaur in his yard and fears he is losing touch with reality. He suspects he might be imagining things or going mad. The event deepens the mystery and motivates him to seek help from his friends.

The next day, Nobita leads everyone to the tunnel, hoping to investigate. Suneo emerges from an exit and claims he saw a herd of dinosaurs, but the others don't believe him. The lack of belief adds tension as they explore further underground.

They go underground again, and Suneo uses a camera to record the plane crash he witnessed earlier. Frightened, he runs into a cave, gets lost, and is captured by a knight riding a dinosaur. The group must react quickly to find a way to rescue him.

Gian's and Nobita's moms become furious when they realize the kids lied to leave the house. The group has to hurry back, and the Anywhere Hole is destroyed by a passing truck. The disruption cuts off their secret path to the underground world.

Doraemon goes to apologize to everyone and discovers Suneo hasn't returned. Nobita and Doraemon watch Suneo's recordings and learn that his plane is still flying inside the underground world. They vow to find him and uncover what is happening.

The group reaches a river entrance to the underworld, but they are captured by native Kappas. A knight named Banhou intervenes and explains that Suneo is in the capital Enriru. The encounter hints at memory-erasure if they return to the surface.

Banhou's sister Roo helps them navigate the underworld, and they visit a museum that shows underworld humans evolved from dinosaurs. They learn that many inhabitants are unaware of the true sky, Sun, and stars. The discoveries deepen the mystery of the underworld's origins.

While riding a dinosaur, Nobita is taken to a forbidden building where he overhears plans to reclaim Earth's surface from mammals. He rushes back to warn the others, and they prepare to flee from danger. The revelation sets up the ship's appearance as a means to escape.

The ship is revealed to be a time machine and whisks them to the Cretaceous era. They witness the asteroid impact and the ensuing tsunami, forcing them to seek shelter underground. After the waters recede, they return to the surface, hailed as heroes with memories intact and their belongings restored from underground.