Ebisu is a young, androgynous woman with a perpetually sullen expression who first shows up in chapter three wearing a skull mask. She's trapped in the Hole with no way to open a door back to the Magic Users' world—the barrier between worlds is blocking her. When she bumps into Caiman and Nikaido, things go badly fast. Caiman cuts off her fingers to shut down her magic, then bites her head before she can get a word in. Fujita bursts through a door behind her in a panic and yanks her straight out of his jaws, but the violent movement messes up her face and head pretty badly.
The aftermath isn't pretty. Ebisu ends up haunted by nightmares and noticeably unhinged. She stays restrained at En's place until Noi heals her fingers and face, but the head trauma stuck around—she's got some brain damage that's supposedly temporary but leaves her acting way more eccentric than before. After that she's constantly hanging around Fujita, enough that fans basically consider them partners now.
Her smoke type hasn't been directly shown, but she's known to be skilled at Reptile transformation. That said, there are hints she's attacked people with way more power than usual after someone gave her Black Powder—apparently someone who'd already met her before. Throughout the manga she basically exists to get beat up and mangled in comedic ways, the running gag being nobody treats her with much dignity.
Content compiled by AnimeList.moe from publicly available sources.