The next day, Mirai Trunks took his guests, except for #17 on a tour of his world. #17 opted to stay at Capsule Corp. because he didn't want the populace to panic when they see him. So the 6 kids said good-bye to Bulma and flew off, Marron on Mirai Trunks' back (since he was their host). Bulma immediately set off to work on a time machine to bring her guests back home. #17 decided to make himself useful by helping with the repair work. (Most of the work was done by robots so they wouldn't freak out when they see him.)
From the sky, Trunks, Goten, Marron, Bra and Pan could see how bleak Mirai Trunks' world was. What used to be cities lay in ruins. Most of the land and vegetation had been destroyed and had only begun the slow process of regeneration. There wasn't a soul for miles around. It was eerily quiet, devoid of all the activities that indicated presence of life that they were so used to in their world.
Presently they came to a small human settlement. Mirai Trunks told them that these days he spent most of his time helping the people rebuild their cities. There were a number of people at the settlement, some with cranes and forklifts, others carrying bricks and pails of cement on their bare shoulders, all working as hard as they could to build their lives again. Mirai Trunks and the others landed nearby and walked to the settlement. The people stopped their work for a while and greeted Mirai Trunks. He returned their greetings and introduced his guests, but didn't tell them where they were from. They didn't press him to tell them, although many of them looked at Trunks strangely. Then Mirai Trunks joined them in their work; effortlessly carrying a ton of bricks and assembled them to build a simple house. Trunks, Goten, Marron, Bra and Pan offered to help too. Soon they were able to rebuild the small town, with enough houses for all the people, and some basic facilities such as water supply which they did by creating a dam on a nearby river. The townspeople were very grateful for their help. Their town, which would've taken months if not years to rebuild was now completed in just 1 day.
They carried on in this manner for the rest of the day. At the end of the day, they were all very tired but happy. Mirai Trunks was very grateful for their help. Even with his Super Saiyajin strength he could only do so much at a time. With the 5 assorted human and Saiyajin hybrids, they got so much more done in a shorter amount of time. The assorted human and Saiyajin hybrids, on the other hand were glad to help. Seeing how hard these people's lives were made them appreciate the comforts of their home, which previously they had pretty much taken for granted.
They returned to Capsule Corp. at sunset to find that #17 had prepared dinner. He told them that after doing the repair work, he went to the woods to hunt. Using his skills as a hunter, (and he was very skilled, because that's what he's been doing for a living all these years since his resurrection after the Cell games) he was able to get a big catch, enough to feed all the hungry Saiyajins. He even cooked the meat himself. It was delicious, and after a hard day's work they were all every hungry anyway and would've eaten just about anything.
Bulma announced that her work was going well, but there were some complications in her calculations. She then went on to describe them in great lengths, but noticed the alarmed looks on the faces of her guests except for her son who was used to her technical ramblings. "Don't worry," she finally said. "It's just a minor setback. I'm sure I could solve that little problem and we'll send you back to your correct timeline at the correct time. I'll just need more time, another week, I think. Your parents won't even know you've been gone."