Originally, Dragon Ball Z established that every Z-Warrior was killed in Trunks’ future. Here’s how Dragon Ball Super retconned that with Yajirobe.
Thanks to a Dragon Ball Super retcon, Yajirobe miraculously survived the battle with the Androids in Trunks’ future. A key part of Dragon Ball Z lore was established with the arrival of Future Trunks, who told Goku about their upcoming battle with Dr. Gero’s creations and the fall of the Z-Warriors, both of which being events that played out in his timeline.
In the story that was told to Goku about what would happen in the future, Future Goku died of a heart virus, forcing the Z-Warriors to face off against the evil Android 17 and Android 18 without him. Because the Androids greatly outclassed them, they were able to decimate all of the Z-Warriors, one by one: Piccolo, Vegeta, Krillin, Tien, Yamcha, Chiaotzu, and Yajirobe were all killed in battle. Master Roshi, who was no longer a member of the Z-Warriors at this point, wasn’t around. As for Gohan, he was able to get away from them and grow stronger. Later on, he became a Super Saiyan and trained Trunks, and the two stuck together until Gohan too perished at the hands of the two Androids. That was when Trunks endeavored to go to the past and prevent this post-apocalyptic future from ever happening.
Several years later, an episode of Dragon Ball Super revisited Trunks’ version of these events by sending Goku and Vegeta to the future to help Trunks battle a new threat. While there, they crossed paths with a familiar face: Yajirobe. Previously, it had been shown that Future Yajirobe was murdered by Android 18’s High-Pressure Energy Wave, but it was revealed through his conversation with Goku, Trunks, and Vegeta that he, despite being the weakest of the Z-Warriors, in fact, survived that attack.
According to him, he was saved by Korin, who gave him the last of the Senzu Beans. In the anime, Senzu Beans are often used by the main characters so that they can quickly recover from injuries sustained in combat, and in this case, the Senzu Bean allowed him to recover from what would have been a fatal wound. Thanks to this decision by Korin, Yajirobe survived in secret, with Trunks falsely believing that he had died alongside all the other Z-Warriors. Years later, Yajirobe joined the Resistance when Goku Black emerged as a villain.
The presence of Future Yajirobe in Dragon Ball Super amounted to a nice surprise. As a character who actively avoids fighting and training, he hasn’t had that much to do in the anime. Prior to Dragon Ball Super’s Future Trunks Saga, the last time he made a real impact on the story was all the way back in the Saiyan Saga, when he leaped out of hiding to cut off Great Ape Vegeta’s tail. This was without a doubt Yajirobe’s biggest moment ever. With that in mind, it was good to see Yajirobe back in play again as a member of the Resistance. Similar to his last-minute efforts against Great Ape Vegeta in Dragon Ball Z, Yajirobe swooped in at a crucial moment to save Goku and Trunks from a deadly attack.