Officers responded to the apartment on Puunani Place after receiving the call at about 9:35 am. Investigators knocked on doors and questioned residents in the area.
Paramedics officially pronounced the 46-year-old man dead at 2:07 pm. Police say the partially-clothed body was found on the floor of the bedroom.
"There was some blood located near him," Maj. Clayton Kau, Honolulu Police Department, said.
An upstairs neighbor told Hawaii News Now that there was a foul odor coming from the unit, so he opened the unlocked door, looked inside, and found the resident with two samurai swords through his chest.
"There was no signs of any type of forced entry," Kau said. "There was no signs of any type of struggle within the apartment. So once again, we're still following up on, we're still working on the investigation."
Neighbors told police the last time they saw the man was about seven days ago.
Investigators are waiting for autopsy results. For now, the case is classified as an unattended death with suspicious circumstances.