Graffiti was found Tuesday morning on a stone wall that surrounds the Akasaka Estate in Tokyo, where Emperor Naruhito and his family reside, police said.
Red lines and writing in the Roman alphabet spanned dozens of meters on the east wall facing the sidewalk. The graffiti, which appeared to have been sprayed on, was reported by a passerby at around 5 a.m., they said.
Similar markings were found on nearby trees and roadside traffic mirrors. Investigators are checking security camera footage in the area, police added.
