Though street crime is relatively low in Japan, quirky camouflage designs like this vending-machine dress are being offered to an increasingly anxious public to hide from would-be assailants.

Take the “manhole bag,” a purse that can hide valuables by unfolding to look like a sewer cover. Lay it on the street with your wallet inside, and unwitting thieves are supposed to walk right by. There is also a line of knife-proof high school uniforms made with the same material as Kevlar, and a book with tips on how to dress even the nerdiest children like “pseudohoodlums” to fend off schoolyard bullies.

“It is just easier for Japanese to hide,” Ms. Tsukioka said. “Making a scene would be too embarrassing.” She said her vending machine disguise was inspired by a trick used by the ancient ninja, who cloaked themselves in black blankets at night.

“Japan is so fashion conscious that just changing the way you dress can make you safer,” Ms. Nakano said. “Culture plays a big role in risk prevention.”