Rogue Lords

You need the character Hecate to obtain this, who is unlocked after completing The book of Charon (3rd book).

She has a ritual as part of her starting move set that allows her to heal your entire team for 7SP every turn.

Load up a book of your choosing, I chose the final book. Make sure you put apprentice mode on so you get 100 demonic essence to play with. Through a combination of demonic essence use and her ritual, you should easily be able to survive 5 turns in order to pop this achievement by simply healing as necessary with demonic essence and ending each turn without attacking anyone to speed things up. Simply load into the first battle with her and do this for 5 turns, and the achievement will pop at the end of the 5th turn.

If you get enemies who do solely spirit damage, you won't even need to use any demonic essence to stay alive unless they do a spirit combo attack, as Hecate's ritual will keep your spirit outside of vulnerability status, which means even if they hit you for more than 7 spirit damage, you won't start losing demonic essence and die from the hit because you don't die from damage unless you're vulnerable when you receive it. That's why it's best to go for this in chapter 1 of a book when the enemies are weaker, as they typically don't use combo attacks until later on in a book.

If you believe anything stated here is incorrect or have better information, please leave a comment so I can improve the solution. Thanks.