The story starts as normal. Until the moss-covered time machine was discovered. After looking into it, Gohan became curious about Trunks'. So he lets him check it out as he goes in as well. He shows and explains to him the mechanics. Unfortunately, this leads to Gohan accidentally pressing one of the buttons, which causes them to go back to 749.
When the boys arrived, Gohan instantly recognized this place as Mount Paozu. However, Trunks tells him that they need to go back into the present. Unfortunately, he realized that the Time Machine was used twice. This means it ran out of fuel, and this was a time when Bulma hadn't invented it yet. So they will have to be stuck there, forever.
Trunks is devastated by this and thinks about what will happen to his timeline. Besides, the thing who used his Time Machine could be a dangerous threat. Gohan burst into tears and hugged him as he apologized for causing the situation. Trunks sighed and told him it was just an accident. The boy has calmed down as Trunks puts his machine back into a capsule. He tells Gohan to keep their identities a secret. Gohan genuinely understands this, whereas Trunks decides to raise him as a little brother. Since Future Gohan was an older brother figure to him.
Meanwhile, in the main timeline, Bulma is determined to find the mystery of the egg. As she looked around to find evidence. She saw the exoskeleton of a giant insect. Like in canon, the dragon team learns about Gingertown's massacre. Along with Kami and Piccolo fusing. They faced off with Cell as the dragon team can feel many power levels at once. He and Piccolo started to fight, and he told about his origin story and how he traveled back in time.
Since the remainder of this part would be the same, we will go back into the past. Anyway, the two Half-Saiyan boys were taking a stroll when they noticed a young child carrying a giant fish. Gohan and Trunks both immediately recognize him as Goku. The kid was amazed to see two humans apart from his grandpa. This made Gohan and Trunks look at each other confused. However, Goku offered them to have dinner in his house. They accept it since they're hungry and don't have a home.
While the three were walking through the trail, they heard a sound coming towards them. Trunks and Gohan jumped into the side for side, but Goku just stood there. Trunks yelled by telling him to get out of the way, but it was too late as a car accidentally bumped into the boy. The girl driving it was horrified, and Trunks sternly told Goku that what he had done was dangerous. Once the girl saw the lavender-haired hunk, she came out of the car and walked towards him. Both of the Saiyan hybrids instantly knew that this was Bulma. However, the teal-haired girl introduced herself and started to flirt with Trunks. This made Trunks feel extremely uncomfortable and told her that he was not interested in any dating.
However, Goku saw this as a threat because he had never seen a girl before and Trunks' discomfort. So, he's about to attack the "goblin" to save his new friend. Trunks stops him and explains that this is a person, not a monster. Goku is unsure about this, and Bulma tells him that she's a girl. The boy was surprised because he had never seen a female before. Gohan and Trunks already figured this out because he had only known one human before he met them. When Goku mentioned his grandfather's death, Gohan started to feel sympathetic towards him. However, he was embarrassed to see Goku do such a perverted act towards Bulma. Before they could walk out, the girl put her car back into her capsule, which horrified Goku.
As the four were walking towards Goku's house, they were introduced to each other's names. Goku was amazed to hear this boy had the same name as his late grandpa. Then Bulma points out that they do look similar, as this was awkward for Gohan. When they arrived, Bulma noticed the four-star Dragon Ball and grabbed it. Gohan instantly recognized it as the one that was on the hat that he used to wear. Just as in the original, Bulma tells everyone about the dragon and convinces Goku to let her have the Dragon Ball. So, the group started their journey as Bulma even let Trunks and Gohan borrow one of her motorcycles. Like the original, Bulma needed to have a potty break but was kidnapped by a pterodactyl. However, Trunks is the one to defeat him by slicing him in half. Bulma was grateful that she was rescued but was horrified by the dinosaur's aftermath. Gohan on the other hand was used to it and it didn't bother Goku.