Thanks to all her knowledge, Bulma has managed to get Trunks' time machine up and running again. You can play Trunks in the end game of Dragon Ball Z, and opens up several sub-stories inaccessible without him.
Lone Guardian
Go to Capsule Corporation as Future Trunks to talk to Bulma. The latter will inform his mother that Future Bulma needs Magidemia seeds, a specific ingredient that can't be found in the future. She will agree to help him and tell him exactly where to find them.
The Magidemia seeds is located in the northern mountain area. The precise location, noted on the map, is near a fishing area and a dinosaur. On the way there, C-17 approaches Trunks, explaining that he has become a ranger but that he would very much like to fight him. This one won't be a big threat, as he's level 49, so it'll be possible to get rid of him in a few minutes.
Once the "friendly" fight is over, C-17 will go get the Magidemia seeds, hand it to you and go on with his work.
In addition to the rewards, including a nice number of D Medals, the C-17 soul emblem will be yours and can easily complete several of your community boards.
