What is a Yandere?

My name is Tanigawa Hiroto, and my nee-chan is a yandere. “Ototo-kun~once you’ve written the synopsis then quickly come and play some embarassing games with mee, I can’t wait anymore alreadyy, I still wanttt some moreee~~” I glanced at the naked figure of Asaka nee-chan lying on the bed and continued writing: Please favourite, like, and rate 10 stars for this novel qwq.

P/N: ototo-kun = younger brother, nee-chan = elder sister
P/N2: this series was originally in CN; the entire plot is set in JP, and was written using JP style. Consider this CN series.