This may be a short story, a novella, or a novel. The story is very simple. The secondary personality protects the main personality. It is considered "self" protection and "mutual" redemption. It has an open ending...
This book is also known as "The Diary of a Bystander" and "The Daily Life of Yuan and An"
Intention: Since you are not loved by others, then learn to love yourself "by yourself"