When Doctor Ryuji becomes the savior for Ai and her sister

Returning to episode 4 with a “happy ending” twist. After seeing her sister Nagi Hikaru with Doctor Ryuji, Ai decided she wanted to experience being a woman too. Instead of his usual dark ways, Ryuji used a new invention to bring pleasure to both sisters, leaving Ai thinking it was all a dream. The story ends with Ryuji moving to the countryside with his new wife Ren, continuing his medical career and his quirky experiments in a peaceful setting.