In the first Munto OVA, the main source of energy in the world, Akuto, is running low. The Magical World in the Heavens uses most of the available Akuto energy, antagonizing the Heavenly people and causing them to unite against the Magical Kingdom. To restore the flow of Akuto and save both the Magical Kingdom and the Heavens, young King Munto decides to follow a vision and find Yumemi, a girl who lives in the "Lower World", Earth. Gass, the Guardian of Time, allows Munto passage to the Lower World, amid the chaos of potential war, to seek the girl of destiny. The prophetress Ryuely and her young apprentice Toche keep watch over Munto as he journeys to Earth.
The girl of destiny is junior-high student Yumemi Hidaka. Ever since she was little, Yumemi has had the ability to see floating islands in the sky, and accepted them as a part of everyday life. However, after unsuccessful attempts to convince her friends and peers of the islands' reality, she fears there is something wrong with her and begins to carry a pink umbrella around everyday to block out the sky.
Munto falls to Earth successfully and manages to find Yumemi as she walks to school with her friends Ichiko and Suzume. Confronting a stricken Yumemi, he tries to convince her that she has a power he needs to save both their worlds to restore the flow of Akuto. In an attempt to get closer, Munto realizes that the space-time continuum prevents him from making further contact. Just as Yumemi is beginning to gather her wits, Ichiko pulls her out of what appeared to be a dreamlike trance, and breaks the conversation with Munto.
Throughout the OVA, Yumemi struggles to differentiate between reality and dreams while Munto appears to her every now and then, pressuring her to use her psychic power to aid him. Yumemi tells him several times that she doesn't know what this power is, and becomes confused and fearful for her sanity. Upon realizing she is the only one who can see Munto, she begins to ignore his requests and tries to shut him out. Her friends worry for her, but the issue is further complicated when childish Suzume voices her plan to marry her delinquent boyfriend, Kazuya. A meeting with Kazuya confirms their intentions, and Yumemi thinks about responsibility and duty, wondering what hers is to Munto. Meanwhile, Munto is getting weaker from staying on Earth for too long and has to battle a droid sent from the Heavens to eliminate him in order to seize control of the Magical Kingdom.
At the climax of the OVA, Suzume and Kazuya go through a trial where they cross a river together, calling this their "marriage." As she witnesses this with Ichiko, Yumemi realizes she must face her own uncertainties and help Munto -- for she sees that the island in the sky is now falling to certain doom. As the Magical Kingdom parts the clouds overhead, it becomes evident to Yumemi that Munto was telling her the truth.
After searching, she finds Munto as he is starting to disintegrate from staying too long in her world, giving up hope after narrowly defeating the droid. Yumemi willingly gives Munto her power by crossing the space-time continuum and touching him. As she does so, the people of Earth can see the island in the sky as well, although temporarily. Ichiko, who secretly desired to see the island since Yumemi mentioned it, has her wish fulfilled. The balance of Akuto is temporarily restored and the story closes as Munto returns to his kingdom. Yumemi can still see islands in the sky, but stops carrying her umbrella as her life goes on, assured that she is not hallucinating but merely psychic, and no longer ashamed of "the part of her that is different," and the OVA closes as she thinks that she and Munto will meet again.
Munto 2: Beyond the Walls of Time takes up about a year since Yumemi last saw Munto. Yumemi often loses herself in gazing at the sky, to the discomfort of some of her friends. She senses that something is wrong up there, because her strange visions of Munto's past, bestowed on her after she and Munto touched, have returned with increasing force and frequency. What Yumemi doesn't know that she's at the center of a new political storm: the heavenly lands are in chaos, its regions battling each other, driven power-mad by the new wave of powerful Akuto.
Yumemi and Munto's roles are reversed in this OVA; Yumemi longs to overcome her earlier weakness and help Munto, but Munto won't risk calling her into his war. Unknown to Munto, though, he's not the only one who needs her power -- and certain others are not nearly so worried about risking her life. Eventually Munto re-enters Yumemi's world, but only after Gass forcefully sends him there, in need of her assistance whether or not he wants to admit it or not. Ichiko plays a bigger role in this OVA, fearfully trying to keep Yumemi a part of her life by pressuring her to forget about the sky she herself has once seen and stay with her friends. Yumemi however, becomes worried and scared as her visions slowly make her realize the vastness of the situation and she despairs at what she should do, all the while losing herself more and more to staring off into space. Finally however, at the moment of crisis when the Heavenly Kingdom begins to fall once more, Yumemi finds Munto and convinces him to accept her help, and with a last goodbye to her friends, they take to the skies together toward the Magical Kingdom.
Kyoto Animation is releasing a third Munto OVA in the near future.