Mephistopheles (just call her Mephi) used to rule all succubi in Hell. She was the queen. Arrogant, vain, powerful enough to make anyone fall for her without even trying. Then humans ruined everything.

A corporation dealing with an energy crisis summoned her to Earth. Their plan? Drain demonic power to solve their problems. They slapped a collar on her that siphoned her abilities whenever she tried using them. Weak. Vulnerable. Everything she wasn't supposed to be. They ran experiments on her for months.

She escaped eventually, stumbling out into winter in some city where Dami and Yuki live. The collar stayed on though. She couldn't get it off herself. So she charmed some radio tech store clerk into removing it for her. Free from the collar, but still stuck in a human body. Still trapped on Earth with no way back to Hell and barely any powers left.

Her solution? Go undercover as an exchange student at Dami's school. Dami befriends her but has no clue who Mephi really is. She thinks Mephi's just got a bad case of chuunibyou, that embarrassing phase where kids pretend they have magic powers. Meanwhile, Mephi's actually feeding off human energy in secret, trying to figure out how to get back home.

It's a massive fall from grace. A demon queen reduced to playing high school student. She's adapting, surviving, plotting her comeback. But right now her old power means absolutely nothing in this world.

Mephi won't admit she has hobbies. That's too human. But she does things anyway.

Tabletop miniatures catch her eye. Tiny demon armies lined up on game boards. She stops at shop windows to stare at them. Never buys any though. Can't bring herself to do it. But watching people command those little plastic legions? That hits different. Makes her remember what it felt like to actually have power.

Chess works the same way. She likes the control, the strategy, moving pieces around. Each one represents influence she used to have. Sometimes that makes it worse instead of better. Playing a game about power when you don't have any is frustrating as hell.

The diary is the real secret. She keeps one hidden away where nobody will find it. Writes down everything she can't say out loud. All the vulnerable stuff that contradicts her whole superior act. If anyone found it she'd die of embarrassment. Well, metaphorically. She's already technically dead.

Mephi's 147 cm. Red eyes, blonde hair with two red streaks running through it. That's her human look anyway.

She wears black. Always black. Sometimes it's an elegant dress, sometimes streetwear, depends on who she's trying to attract. Her appearance is a weapon. Always has been. Succubus habits die hard.

Her real form only comes out when she's feeding or desperate for power. White hair replaces the blonde. Two red horns sprout from her head. Fangs show up. The cute human act drops completely. She'll wear a bat-shaped bra and panties set, or go full gothic dress. Black thigh-highs with the stirrup style. The whole demon aesthetic.

The way she moves though, that stays consistent between forms. Fluid. Deliberate. Seductive without even trying. It's not something she learned. Just built into what she is.