Nobita finds a small plant still in a container at an abandoned area and decides to take it home. His mother asks him not to put it on their garden because it won't have space to properly grow. Therefore he asks Doraemon for help. The robot cat then uses a special plant converter from the future that will allow the plant to move freely without the need to form roots attached to the ground. Named "Kibou" (Hope), the small green creature gleefully plays with Nobita and his friends. The group is taken by surprise when they are suddenly transported to another planet governed by a society of plant beings. Doraemon and his friends then discover that due to mankind's mistreatment of nature, the green population is planning to remove all plants from Earth. They must now return home and find a way to save the world.