Yakuza 6: The Song of Life

This achievement can be unlocked as early as Chapter 1, as there are 11 substories that are available, of which all but one (that being A Man Rises Up, which can't be completed at the earliest until Chapter 6.) can be completed here. Of these 10, half of them are related to the cabaret club hostess minigame, with each one tied to one of the five hostesses at the Club Shine on Pink Street.

To unlock these substories for access to completion, you have to raise the "Love Value" rank for each girl (Saki, Riona, Erina, Hikaru, and Sora) to the maximum rank of 'Diamond'. You can earn points to the Love Value rank through actions leading up to and during the conversation minigame with the hostess of your choice, ranging from requesting a specific hostess by name, to requesting for that same hostess two times in a row, unlocking information on a hostess' profile, as well as from extending sessions after the six actions you're offered in terms of conversation cards to raise a hostess' Heart Gauge, located at the top left corner of the screen, are used up. You'll want to fill that gauge entirely (you've got the six actions to start, as well as two session extension offers with two actions each to accomplish this), as that will give you 13 Love Value points for an 'Excellent' ranking (as opposed to just 5 points on a 'Good' rank if you end your session with any portion of the bar still unfilled. On another note, you can get 18 points if you fill up the bar without needing to extend your session to do so for a 'Perfect' rank, though from my experience it's more probable to achieve this for the session with the hostess after your subsequent date with them, which you then can get a handy Heart Gauge bonus that fills half of your first bar before your session starts.) You'll need 150 "Love Value" points to get the Diamond rank, and afterwards you'll get a text on your phone from your hostess asking them to come to their requested location, from which their substory can begin.

I've attached CyricZ's strategy guide on how to best utilize the offerings in the Cabaret Club minigame in terms of both preparation as well as efficiency so that the player can complete each hostess' substory as quick as possible. (https://gamefaqs.gamespot.com/ps4/181153-yakuza-6-the-song-o...)

That told, the 10 substories that can be completed in Chapter 1 and therefore unlock this achievement are as follows:

Haruka's Biggest Fan
I, Hiji
Face Your Fears (unlocked from Saki)
Hostess with a Heart of Gold (unlocked from Riona)
Caught in a Love Triangle (unlocked from Erina)
Listen to your Heart (unlocked from Sora)
A Shady Business (unlocked from Hikaru)
Look What The Dragon Dragged In
The Temptation of Live Chat
We're Committed To Results (Must finish one session of the RIZAP Challenge, consisting of two exercise minigames, then eating a food item from a restaurant that best fits the description from Makuta. Consume the food and then report back to Makuta inside RIZAP [located where Mach Bowl used to be, on Theater Alley] to get the results from the challenge, and the substory will be complete.)

Once again, credit goes out to CyricZ. (https://gamefaqs.gamespot.com/ps4/181153-yakuza-6-the-song-o...)