病が治った完璧すぎる幼馴染に徐々に外堀を埋められていた件

The protagonist, Nagisa Rokudo, once died and was reincarnated.

It wasn’t a different world reincarnation or a modern fantasy reincarnation, but a place that closely resembled the world he originally lived in.

Although there was a slight disappointment, Nagisa had a childhood friend in this world.

She was cute, beautiful, smart—a perfect childhood friend.

However, she fell ill and couldn’t move her body properly.

But by some stroke of luck, a miracle happened, and the childhood friend recovered and became lively again.

And—quietly and unnoticed—she had transformed into a yandere who harbored a demon within her.