One day during summer vacation, a palm-sized alien named Papi appears from a small rocket that Nobita picks up. He is the president of Pirika, a small planet in outer space, and has come to Earth to escape the rebels. Doraemon and his friends are puzzled by Papi’s small size, but as they play together using the secret tool “Small Light”, they gradually become friends. However, a whale-shaped space battleship comes to earth and attacks Doraemon, Nobita and the others in order to capture Papi. Feeling responsible for getting everyone involved, Papi tries to stand up to the rebels. Doraemon and his friends leave for the planet Pirika to protect their dear friend and his home.

Nobita, Gian, Shizuka, and Suneo is preparing for a school play on the "Journey to the West". As they are arguing about who should play the role of the monkey king, Nobita suggested that the real monkey king should play the role. Because the monkey king is only a legend, Nobita and Doraemon have decided to go back in time using the time machine and make a fake one and show Gian, Shizuka, and Suneo to prove that they are right. Unfortunately, Doraemon's machine allowed the fictional monsters to come to the real world and defeated the entire human races, thus turning the future (Nobita's time) into a demon-ruled world. In order to reverse the change, Doraemon and gang needed to return to the past and capture the demons back into the machine. On the way, they have met the real monk and rinrei (a child). At the end, they have either returned the demons back to the machine or destroy them with Dorami's help, thus turning the future back to normal.

Nobita requests of Doraemon the Moshimo-box and wishes for the world to become a place where the use of magic is possible. Witchcraft replaces science and technology and everyone makes use of it on their daily lives, except for Nobita, who, like usual, isn't very good at conjuring spells. Frustrated, he plans on returning things to their past state, but his mother threw the Moshimo-box away.

Educational video produced by the New Energy and Industrial Technology Development Organization (NEDO) in 1994, it was later included on the 13th issue of Boku, Doraemon magazine released on August 20, 2004.

The movie starts with Dekisugi expressing his love to Shizuka which makes Nobita cry (even though it was a rehearsal for a play in Nobita's school—Nobita thought that it could influence Shizuka to marry Dekisugi). He goes to Doraemon, asking him to take him to the future to see if he and Shizuka will marry