This achievement is unlocked for completing the Truthful route. The Truthful route is not available from the start of the game and is only unlocked in new game plus. To get it you must keep everyone alive to the end of the game. At the end of your first game you will be notified that you could have saved
if you raised your affinity with them so save your clear data, load it and begin the game again, this time make sure to invest heavily in
and ensure all your interactions with them increase their affinity.
Full achievement guide:
https://www.perfpara.com/post/digimon-survive-trophy-achieve...Full achievement walkthrough:
https://www.perfpara.com/post/digimon-survive-trophy-achieve...