About 6,600 police officers are now engaged in a fruitless manhunt for 27-year-old Tatsuma Hirao, who was serving time for multiple thefts, according to officials.
The case is making headline news in Japan with TV channels picking over the manhunt in minute detail.
Hirao gave guards the slip on April 8, vanishing from the facility, an "open institution" where inmates can walk around freely.
Police have detected the fugitive's fingerprints and several thefts have been reported since his escape but he remains on the lam.
The stolen items include socks, a mobile phone, a wallet, a pair of sandals and a car key, whose owner found a polite note -- apparently from the fugitive -- saying: "I'm borrowing your car but I'll never damage it."
The country's justice minister felt the need to apologise for the difficulties in recapturing the criminal, saying: "I heard the incident has caused anxiety among local residents, especially since there are many elderly people living alone... I feel truly sorry."
The minister, Yoko Kawakami, added that 96 prison officers had been assigned around the clock to protect schools on Mukaishima island in southwestern Japan, where the fugitive is believed to be hiding.
The hilly landscape also prevents officers from spotting the convict from a helicopter, the paper said.
The island is about 22 square kilometers in area with a population of around 22,000.
"Terror and anxiety on a peaceful island," headlined Fuji TV, presenting a panel discussion about the case.
A total of 21 inmates have escaped since the opening of the prison in 1961.
Japan enjoys one of the lowest crime rates in the developed world but has a relatively high re-offending rate.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)