As Trunks, go directly to Capsule Corporation after the fight against Kid Buu. Bulma will be near the entrance and she'll ask you to do something for her in this secondary story of Dragon Ball Z: Kakarot.
The Sins of the Father
A party is organized with all of Bulma's friends on the island of Master Roshi, as an opportunity to remember all the memories of the adventures lived together. Unfortunately, Vegeta's wife will not be able to go there due to a last minute hindrance. It will be up to Trunks to go there. Once in the old master's house, everyone's stories will unfold until the next morning. The young visitor from the future will be led to ask questions about his father and will learn everything he has done in the past.
The next day, back at Capsule Corporation, Trunks will tell Bulma what he has learned, which will reassure him about his father's current nature. Vegeta will come to meet them and offer Trunks a training session, as a way for him to express his feelings. The fight will go smoothly, Vegeta being level 53.
