Satte Mayor Kunio Watanabe, 62, was in a bar alone at about 2:30 a.m. when he punched the 20-year-old woman, police allege according to Japan Today. Watanabe was in Hiroshima to take part in a ceremony commemorating the 74th anniversary of the day the U.S. dropped the nuclear bomb on the city during World War II.
Japan Today reports Watanabe said he was drunk, didn't remember punching the employee and couldn't understand how he could have committed the assault.
Watanabe was elected mayor of Satte, which is less than 40 miles north of Tokyo, in 2011 and is serving his second term, according to Japan Today. Police said he and the woman didn't know each other.
Fox News' Tyler Olson contributed to this report.