Please Kill Me, Holy Maiden

Tina was given a mission by a system: protect the heroine, Miss Shatiya.

Later, she was framed, betrayed, and executed, dying in front of Shatiya.

She thought that once the mission was completed, she would be able to leave this world, but what did "failed to exit" mean, hey?

And so, her consciousness became lodged in her dead body.

Just then, the heroine Shatiya regretted it.

To bring her back to life, Shatiya guarded her motionless body for 79 years.

By the time everything had changed, she too had strayed onto the wrong path and become an obsessive yandere, even falling into demonic corruption and dying at the hands of humans.

Why did she have to love me this much? Am I worthy of being loved?

Then, through time travel, Tina and Shatiya both returned to the starting point of their grievances and entanglements.

This time, Tina will use everything she has to protect the fallen yandere heroine.

But for some reason...

Why are they the ones calling me a yandere instead?

...

This book is also titled: "To Protect the Heroine, I Became a Yandere"