Dragon Ball Z Kakarot is cut into arcs, themselves cut into episodes and each one is a new opportunity to come across new sub stories. These sub-stories are very important if you want to collect all the emblems of the game, so you'll have to do them all in order or you'll get stuck.
Note: This article will of course be updated regularly with more sub-stories.
Don't miss out on a side story
As mentioned above, many of the sub-stories require completion at a time T, with no possible turnaround. There is a very simple way to see which subquests are available from the History menu. Navigate between the tabs until you reach the tab dedicated to the available subquests, and you will then see the list and position of the subquests.
Stop The Saiyan Invasion Substories Guide
Episode 2 - Rumble with Radditz
If you set your sights on completing all of the secondary missions and reaping not only some great experience, but also a few D medals and a whole bunch of ingredients, you'll have to stay alert throughout your game. We also recommend that you take advantage of the journeys imposed by these quests to eliminate a few evil enemies along the way, as this will unlock the battle against Mira at the end of the game.
Trunks Time Machine
This mechanism has not yet been integrated into the game, but it will allow you to go back in time in search of secondary stories that you might have missed while browsing through the history of the game.
If you've embarked on the DBZ Kakarot adventure on PS4 or Xbox One, then you may have noticed that the loading times between zones were particularly long. This should be fixed in a future update.