This reminder is from Hachiro on 3 June 2015.
The following text and photos are from Wikipedia:
“Okinawa Memorial Day (慰霊の日 Irei no Hi?, lit. “the day to console the dead”) is a public holiday observed in Japan’s Okinawa Prefecture annually on June 23 to remember the lives lost during the Battle of Okinawa. It is not celebrated nationally throughout Japan.”