Yakuza 4 Remastered

There are 63 substories in the game. Each character has 16 substories, with the exception of Saejima who has 15. Many of them involve simply talking to a character, buying/finding an item, or beating up a group of thugs. Some are more involved though.

If you miss any of a character's substories during the main game, you will be able to play as them again during the Finale and after finishing the game in "Premium Adventure", so don't worry. Also, one of Saejima's and three of Kiryu's aren't available until the finale anyway. Some stories can have a "bad" ending, where the outcome is less desirable and the reward is reduced. These are still considered "finished", so it cannot be missed.

After 20, the achievement is yours. If you are being extra thorough, this can be unlocked during Saejima's Ch. 3.

Full substory guide here:
https://gamefaqs.gamespot.com/ps4/239456-yakuza-4-remastered...

Credit to CyricZ