All endings are the way you play Ayame and make her to be - You determine her fate.
Meaning all routes is their own, and have their own separate ending including story and a scene/CG.
The only ending that will "carry over" is the "true ending via purity route"
As an Example: If you played the family route - The Sato story never unfolded along side or any other for that matter.
This is explained in the beginning of the game - its referred to as "The Multiverse" ingame via the very start.
This was just a quick explanation from me that is not the best perhaps.
Starke have explained this in detail via the discord several times also.
Or somebody else here in the thread may be so kind to give a more detailed explanation