Taimanin Asagi

One of Japan's elite Taimanin, Asagi Igawa has spent years doing dangerous work and now just wants a quiet life with her fiancé. She's earned it — she's one of Japan's elite Taimanin, a covert unit of female ninjas tasked with keeping the peace between humans and demons in a near-future Tokyo where both species uneasily share the same streets. The problem is, the person she thought she'd killed is very much alive and very much holding a grudge. When her arch-nemesis Oboro resurfaces, Asagi gets pulled back into the shadows alongside her younger sister Sakura, who's still early in her own Taimanin career. The setup has genuine tension — a woman trying to leave a dangerous life behind, a sister she wants to protect, and an enemy who knows exactly how to hit her where it hurts. If you've seen Kuroinu or La Blue Girl, you already know this OVA sits firmly in adult horror-action territory, so go in with clear expectations. The ninja-versus-demons premise gives it more plot structure than most entries in the genre, and the character dynamics between the two sisters add a layer that keeps it from being purely gratuitous. Dark atmosphere, supernatural action, and a story that doesn't entirely abandon its characters in favor of shock value. Four episodes, based on a visual novel — treat it as a self-contained dark fantasy that happens to have explicit content woven throughout.