Fukubiki! Triangle: Futaba wa Atafuta ♥

Completely infatuated with Ushio — her older sister's boyfriend — Futaba Shinonome has made it her mission to pursue him, even as he keeps turning her down flat. Respectable of him, honestly. But Futaba is not the type to take no for an answer, and when patience runs out, she slips an aphrodisiac into his drink to force the situation. That decision, predictably, does not go the way she planned. This single-episode OVA from studio PoRO is an adaptation of a Blue Gale visual novel, and it leans hard into the taboo angle — forbidden attraction, complicated loyalties, and the messy fallout when someone crosses a line they can't uncross. The character dynamics are the main draw here; there's genuine tension built around the sister's boyfriend setup before things escalate, which gives it more of a narrative hook than you might expect from a one-episode runtime. If you've watched Oni Chichi or Ane Yome Quartet and appreciated titles that build some character context around the scenario rather than skipping straight to the action, this sits comfortably in that same space. It's also worth noting the production quality holds up well for its 2015 release date — PoRO put care into the visuals. At one episode, it's a tight, focused story that doesn't overstay its welcome. Go in knowing the premise, because the aphrodisiac-and-consequences setup is very much the point.