Digimon Survive

To start the harmonious route, at the end of chapter 8 during the "forked path" you must pick "Be true to my friends." You will be prompted to save right before this choice. You do not need to have harmony as your highest stat but is recommended.

This will unlock once you have reached the end of the story and the credits begin to roll. You may also reload your save from the fork in the road and pick another path without having to start over the game, although this is not recommended because each route will unlock specific evolutions for one of your partners adding them to your "encountered" list.

This achievement starts at the end of Chapter 8 by choosing "Save the World" and will unlock at the end of Chapter 12. You need Harmony as your highest or second Karma Value.
There are some misleading infos about this achievement saying that you need to pick "Be true to my friends". This option is a red one, meaning a MORAL ROUTE not the HARMONY ROUTE.

TIPS FOR THIS ROUTE/MAJOR SPOILER
Don't train Syakomon or Dracmon. Dracmon will betray the team with Kaito and Miu will die, so the team will be Agumon, Falcomon, Labramon and Floramon. Focus on Agumon and Falcomon, get the other two with a reasonable strength but don't forget to train two free monsters to back you up when you are alone. Renamon will join the team after the Library part but will die after Boltboutamon's fight, so don't train her.

There are three main routes and a true route in this game. The three main routes are divided by Moral, Harmony and Wrathful. Many decisions in this game will offer you three choices with each of them increasing one of these three stats. Thankfully, you can tell which one will be increased by the way it's presented. In Karma choices, the left option will always increase Moral, the middle (top) will always increase Wrathful and the right will always increase Harmony. The game will notify you if any of these increase in the top right corner.

You can check your Karma stats by opening the pause menu and clicking Profile. Whatever one of these three stats is the highest is the route you will diverge on to later in the game.

For this achievement you need to ensure that Harmony is the highest by choosing the right option as much as possible. It doesn't matter if you mess it up and add points to other categories you just need to make sure the one you want is the highest. The achievement will unlock once you complete the game.

Full achievement guide:
https://www.perfpara.com/post/digimon-survive-trophy-achieve...

Full achievement walkthrough:
https://www.perfpara.com/post/digimon-survive-trophy-achieve...