Tentacle and Witches

What's the last thing a teenage boy expects to discover about his homeroom teacher? That she's secretly a witch living in a mansion on the hill — and instead of doing the sensible thing and minding his business, Ichirou keeps sneaking around to watch her practice magic. When a classmate named Lily — also a witch — catches him snooping, she decides to punish him by casting a spell to make him her obedient familiar. The spell goes sideways. Instead of a compliant servant, she gets Ichirou partially transformed into a tentacle creature who now needs to absorb magical energy from witches just to stay human. That dynamic — Ichirou stuck between Lily and Yuuko, all three of them tangled up in the consequences of a backfired spell — is the core of what this 4-episode OVA from 2011 is doing. It leans hard into hentai territory, so go in knowing that upfront. The supernatural framing gives it slightly more texture than most entries in the genre; there are actual character relationships and a loose plot threading through the explicit content rather than just scene-to-scene setups. If you enjoyed something like La Blue Girl or Angel of Darkness and want a shorter, more contained story with a consistent cast, this scratches a similar itch. It is not trying to be Izetta: The Last Witch in terms of plot depth, but it has more connective tissue than you might expect from something this short.