Nearly 10,000 people have signed an online petition demanding Amazon remove a bootleg T-shirt with the slogan "Keep Calm and Kill Your Teacher," inspired by Yūsei Matsui's popular manga Assassination Classroom.

Debuting in 2012 in Weekly Shonen Jump, the supernatural comedy-adventure centers on a class of misfits devoted to killing their new teacher, an alien octopus with incredible powers who has just destroyed most of the moon and is threatening to do the same to Earth.

The petition, launched last week on Change.org by Brooklyn resident Christine Russo, refers to the shirt "highly offensive," and calls on the retail giant to stop selling it immediately. "Teachers are the ones protecting students when crazed gunmen come into their school," Russo wrote, "and now they think students should kill them?"

A play on the ubiquitous "Keep Calm and Carry On" merchandise, the shirt features the signature smiley face of Assassination Classroom's teacher Korosensei, used on the manga's covers, in advertising for the anime and live-action adaptations, and on plenty of licensed merchandise. Amazon lists 10 pages of (presumably) official Assassination Classroom apparel and accessories -- from backpacks to T-shirts to cosplay costumes -- but none features a "Kill Your Teacher" slogan. Some, however, do depict students brandishing weapons.

As Time Warner Cable News reports, this bootleg shirt has even drawn the attention, and the outrage, of New York State Assemblyman Angelo Santabarbara, who said he warned local school districts last week about the slogan. He also contacted Amazon, but didn't receive a response.

“Certainly when children are exposed to messages like this it instills fear," he said. "It doesn’t help to create a positive learning environment."

Assassination Classroom is published in North America by Viz Media.

(via Crunchyroll)