Jitaku Keibiin (2019)

Two decades of military and intelligence training have made Kareki Tsunetaka the kind of guy who notices everything, records everything, and misses nothing — and he works private home security. His latest assignment comes straight from his own father: move in and keep watch over his dad's new girlfriend, a woman being considered as a potential bride. Seems straightforward enough. Except Tsunetaka is very thorough, and living in the same house means he sees a lot more than your average security detail would. This 4-episode OVA from Suzuki Mirano leans hard into the surveillance angle as its central hook — the hidden cameras, the intelligence gathering, the clinical detachment of a trained operative slowly getting pulled into something far more personal. The family dynamic underneath it all gives the setup a layer of tension that separates it from a lot of similar titles. If you've watched something like Ane to Boin or Isaku and wanted a bit more of a character-driven setup before things escalate, this scratches that itch. Fans of Jiburiru: The Devil Angel who appreciate when a hentai actually bothers with premise-building will find the first couple of episodes genuinely set the table well. The character art is detailed and expressive, and the source visual novel gives the writing more structure than you'd typically expect. It's not deep drama, but it's got enough going on contextually to keep things interesting between the explicit content.