Talk:Senpai/@comment-35486628-20170102231945/@comment-1915363-20170105141540

Through a single act of kindness to her, the forbidden fruit that people called "emotion" that was previously locked away began to sprout inside her heart and colored her previously empty and aimless life.

That kindness saved her from her emptiness and unlocked her emotion, and like a drug addict, she yearns to experience more of that emotion, but she needed to be near Senpai to do so. So it's less about Yandere-chan fell in love with him for who he is as to treating him as the "precious key" to her forbidden garden of emotion sealed deep within her heart.