At around 5:50 p.m., a woman alerted police after seeing the body floating in Lake Shitsu, located in the Okubo-Minami area.
Officers from the Izumi Sano Police Station arriving at the scene found the body lying face-down in the water. The body had a stab wound to the back.
Due to the stage of decay, the person is believed to have died at least one week ago. The gender of the person, who stood about 170 centimeters tall, is unknown.
Police are now seeking to identify the body and determine the cause of death. The case is being treated as a suicide or the result of foul play.
