My older sister, who has been muddy, is hazy and unable to distinguish between reality and dreams. A younger brother who repeats obscene mischief to such an older sister. And as a result of escalating, it develops into forbidden incest. An older sister who resolutely tries to act as an "older sister", an older sister who becomes an outlet for her younger brother's libido while almost unconscious, and an older sister who gets drunk and horny and has sex with her brother.
