Reborn as the False Master of a Truly Yandere Disciple

If she had to transmigrate, why did she have to transmigrate into a book? And what’s with this yandere who could die on you at any second? She’s transmigrated into the role of a fake master, pretending to be someone she’s not all day while constantly worrying that her little disciple only has a few hours left to live. On top of that, she has to keep filling her yandere disciple’s head with positive thoughts. That would be bad enough, but who can tell her why, after only a few years apart, her disciple has become a great demon lord feared by everyone? So much for staying positive. So much for living to a ripe old age. And what’s with the villainous demon lord pushing her onto the bed? This world has gone completely crazy...