On an unknown world, a young
humanoid is crushed to death by a gigantic
monster which then vanishes as an unseen entity laughs and announces that it is headed for Earth. On Earth,
Gohan and
Videl, acting as their
superhero personas Great Saiyaman and Great Saiyaman 2, stop an elderly man from committing suicide. The man introduces himself as Hoi and presents them with an enchanted
music box, claiming that a hero named Tapion is trapped inside and is their only chance to stop an approaching evil. With all other methods of potentially opening the box exhausted, the
magical Dragon Balls are assembled and a wish to the eternal dragon
Shenron is used to open it. Tapion is released but expresses anger at having been freed, explaining that inside of him is half of the ferocious monster called Hirudegarn that only the box was keeping at bay. Tapion flees into isolation but is visited by
Trunks who takes a liking to him. The lower half of Hirudegarn soon appears and begins attacking the city. Gohan and Videl attempt to fight it with Gohan learning that Hirudegarn is intangible except when it attacks. The fight ensues until Tapion plays a tune on his
ocarina which weakens Hirudegarn and causes it to vanish. Hoi claims that Tapion is the true threat and that the ocarina must be destroyed, so he attempts to steal the instrument and in the ensuing scuffle, Trunks takes possession of it and chooses to side with Tapion. Hoi flees and Tapion accepts Trunks as a friend. Tapion relays his story to
Bulma and explains that one-thousand years prior an evil race of alien
sorcerers set out to destroy all life in the universe by awakening Hirudegarn. Their conquest eventually brought them to Tapion's planet where during the battle, a priest created an enchanted sword and two ocarinas capable of stopping Hirudegarn. Tapion and his younger brother Minotia kept the monster at bay with the ocarinas while the priest cleaved it in half with the sword. In the aftermath, a
war council decided to have Hirudegarn's two halves sealed inside of Tapion and Minotia and have them locked inside enchanted music boxes to be sent to opposite ends of the universe. Hoi, one of the surviving sorcerers, found and killed Minotia and now seeks Tapion's in order to complete Hirudegarn's revival. Bulma builds Tapion a specialized bedroom so that he can sleep without the monster escaping. However, this fails. The monster's lower half reappears and in desperation, Tapion begs for death in order to destroy Hirudegarn's upper half, but the beast manages to escape. Its revival complete, Hirudegarn lays waste to the city and is confronted by Super Saiyan
Goku, Ultimate Gohan, and Super Saiyan
Goten who are no match for the monster.
Vegeta arrives to join the fight in Super Saiyan form but is quickly defeated as well while Super Saiyan Trunks and Goten fuse into
Super Saiyan 3 Gotenks and bombard Hirudegarn with
energy blasts. Hirudegarn then transforms into a more powerful form and defeats Gotenks effortlessly. Tapion attempts to seal Hirudegarn inside of himself again by playing the ocarina and asks Trunks to kill him with the sword once he does. Trunks hesitates and Hirudegarn escapes yet again, destroying the ocarina in the process. As Hoi gloats over his apparent victory, he is crushed to death by the monster. A rampage Goku transforms to Super Saiyan 3 and prepares for one final battle with Hirudegarn. Trunks intervenes and cuts the monster's tail off with the sword and Goku figures out that the monster is only vulnerable after attacking and he takes a beating while antagonizing Hirudegarn. An enraged Hirudegarn is weakened allowing Goku uses his Dragon Fist attack to finally kill it. Tapion uses Bulma's
time machine to return to his planet before it was destroyed. Before departing, Tapion presents Trunks with his sword as a farewell gift. In the
ending credits,
Future Trunks is shown slaying
Frieza with a similar sword. ==Cast==