Mystery Revealed (ボクの父はベジータです... 謎の少年の告白, Boku no Chichi wa Bejiita desu... Nazo no Syonen no Kokuhaku) is the fifth episode of the Trunks Saga and the one hundred twenty-second overall episode in the uncut Dragon Ball Z series. The episode first aired on January 15, 1992. Its original American air date was September 8, 2000.
Goku shares a warm welcome with his friends and appears surprised to see that Frieza and King Cold, who he sensed racing him to Earth in space have been defeated. As he asks who it was, Piccolo points out the mysterious boy, claiming him to be a Super Saiyan. While Goku is astonished, as well as never having met the boy, Vegeta irritably reminds him that they and Gohan are the only three remaining Saiyans left. The boy asks Goku to have a word alone, to the others' surprise, and Goku agrees.
Once alone, Goku mentions that he could have beaten Frieza and King Cold to Earth and defeated them by teleporting himself there with a new technique he learned on the Planet Yardrat, which irritates the boy slightly. The boy then goes onto ask Goku to transform into a Super Saiyan. Goku accepts, and his friends see him power up to his new form for the first time, astonishing them. The boy also goes Super Saiyan and attacks Goku with his sword, but Goku effortlessly blocks him with his forefinger, impressing the boy.
After seeing Goku's potential, the boy introduces himself as Future Trunks, the son of Future Vegeta, having traveled twenty years into the past. Though Goku is amazed at the mere thought of Vegeta being a father, Future Trunks goes on to explain the real reason of why he came: three years from now, a pair of diabolical Androids created by Dr. Gero, a rogue scientist who worked for the Red Ribbon Army, will appear and cause mayhem and destruction on an island nine miles (nine kilometers in the Japanese version) west of South City. By the time of Future Trunks' age, the Earth has been reduced to ruins with only a third of the population left, and that portion is constantly living in fear of the Androids' next attack. The Z Fighters have all been killed in action, and the only two left are Future Trunks and his mentor, Future Gohan, who eventually ends up killed by the Androids and the Dragon Balls will permanently disappear meaning that no one can be revived again after Future Piccolo is killed. Future Goku, however, does not die in battle, but catches a viral heart disease and passes away a few months before. Despite Future Trunks' description, Goku is distraught that he will not be able to fight the Androids. Impressed by Goku's determination, Future Trunks hands him a bottle containing the antidote for the heart disease, which does not exist in the present time. Goku then asks the boy who his mother is, and Future Trunks tells it is Future Bulma, giving Goku another shock causing him to fall over. Future Trunks tells him that she broke up with Future Yamcha for good after she grew tired of him, so she sees Future Vegeta all alone and begins to cheer him up. He asks Goku not to tell anyone about his origins on the basis that Vegeta and Bulma may not conceive Trunks, erasing him from existence. Goku agrees and Future Trunks returns to his timeline in his Time Machine.
Goku reunites with his friends, and Piccolo relays the story, having heard the entire conversation with his superior hearing, but does not say anything about Trunks or his parentage. Goku and the others vow to stick together and prepare themselves for the Androids' attack.
- Future Trunks (Super Saiyan) vs. Goku (Super Saiyan)