This is a Japanese “STOP” sign and it means what all traffic STOP signs mean all over the world… you must stop your car’s movement completely before you proceed.
STOP signs in almost every other country are red octagonal signs with thin white borders and the word STOP or ARRET or the local language word for “stop” in large white lettering in the center.
In preparation for an influx of foreign visitors for the 2020 Tokyo Olympics, there is an initiative underway in Japan to add the English word STOP underneath the Japanese writing in the center of the sign. Luckily.
Japan Tourist Tips 