Aneki no Kounai Kaikinbi

Returning home one day, Anna Hirose discovers her younger brother has been getting too familiar with her underwear drawer. Instead of just yelling at him or pretending it never happened, she makes a decision that sets the entire premise in motion: she's going to handle this herself, older-sister style. That means letting things escalate in ways that are, to put it plainly, way past what most families would consider responsible guidance. The whole thing unfolds in a single episode, so there's no slow burn — it moves fast and stays focused on this one increasingly complicated domestic situation between two adults sharing a house. The tone is exactly what you'd expect from the genre: explicit, unapologetic, and built around a taboo dynamic that the story leans into rather than shies away from. Anna keeps telling herself there are limits, and watching those limits get tested is basically the whole arc. If you've seen something like Oni Chichi or drifted through Imouto Paradise, you already have a rough map of the territory here. It's a similar flavor — domestic setting, family-adjacent tension, escalating situations. At one episode, it's a short commitment, and it doesn't pretend to be anything other than what it is. If taboo sibling dynamics in explicit hentai OVAs are something you're already into, this fits that niche without much padding or setup getting in the way.