The manga received an Original Video Animation in 1991, which has the dubious honor of being one of the last works by Nikkatsu Corporation before its closure.
Not to be confused with Black Cat.
This series provides examples of:
- All Men Are Perverts: Miss Ogawa starts undressing and forcing herself on top of him while hypnotizing him in order to try to get his true identity. Ryoi becomes visibly aroused, and it's only thanks to his brother's interruption that he snaps. Even afterwards, he can only comment on how beautiful she was despite everything.
- Ambiguously Human: It's never revealed whether the brothers are humans endowed with supernatural powers or supernatural creatures who can take human forms. Judging for the last line of the OVA, it seems they ignore it themselves.
- Animal Eyes: Hyoi has slit pupils, just like a cat.
- Animorphism: The main trait of the Dark Cats is turning into cats (apparently regular ones, telepathy aside). Reflecting their personalities, Hyoi becomes a black cat while Ryoi turns into a calico.
- As Long as There Is Evil: Jukokubo says to Hyoi when the latter defeats him.
- Big Damn Heroes: Hyoi bursts into Miss Ogawa's office to save Ryoi.
- Body Horror: The demons take the shape of fleshy, tumor-like tentacled growths, some of them pretty phallic in shape.
- Break the Cutie: Aimi Koenji is put through hell.
- Cool Sword: The Dark Cat Sword used by the brothers. It can turn into a pendant.
- Devour the Dragon: Jukokubo eats Miss Ogawa (or rather, the demon she had become) to power himself up.
- Face Full of Alien Wing-Wong: Having Ryoi hypnotized, Miss Ogawa sprouts a phallus-shaped demon out of her mouth and is about to infect him through his by kissing him, although Hyoi bursts in before it happens.
- Hair Intakes: Hyoi's hair resemble cat ears.
- I Have Boobs, You Must Obey!: Miss Ogawa undoes her shirt before hypnotizing Ryoi, and it seems to play as much of a role on him becoming mesmerized.
- Heroic Sacrifice: Hiroki Koizumi ends with the demon menace by walking into the mass Aimi has turned into and telling her his true feelings.
- Immortal Immaturity: The brothers are implied to very old despite their entities, but Ryoi behaves much like the timid teenage boy he looks like, down to the Sacred First Kiss trope.
- I See Dead People: An ability of the Dark Cats, which is used by Hyoi to exorcise the ghost of a girl in the prologue of the OVA.
- Mind-Control Eyes: When interrogated by Miss Ogawa, Ryoi tries to use hypnosis on her to convince her he is just a regular student. Much to his surprise, it fails, and then it's Ogawa who hypnotizes him, revealing she is demon-possessed.
- New Transfer Student: The Kagezaki brothers play this to investigate in schools.
- Psychic Powers: Dark Cats can use mind control and a minor form of flight.
- One-Winged Angel: Jukokubo can abandon his relatively humanoid form and turn into a giant monster cat.
- Really 700 Years Old: Although they resemble middle/high schoolers in their human form, the brothers's age is implied to be very ancient. Hyoi mentions that they have been fighting Jukokubo for centuries.
- Sadist Teacher: Demon-possessed teachers like Ogawa and Iwata enjoy tormenting their students. It also includes Principal Nishimura, although in his case he is a sadist teacher without any need for possession, as he is actually Jukokubo.
- Shapeshifting Excludes Clothing: Played with. As seen when Ryoi transforms from cat to human in the OVA, he turns first into a nude human and then clothes appear on him, implying that the trope is played straight and that their clothes are materialized through magic.
- Sibling Yin-Yang: Hyoi, the older brother, is cool and professional, while Ryoi, the younger, is more emotional and naive.
- The Vamp: Miss Ogawa seduces Ryoi using both her body and her powers.
- We Will Meet Again: Hyoi says in response to Jukokubo's As Long as There Is Evil.
