The Topix index slipped 1.77 points, or 0.20 percent, to 867.61. Investors were also cautiously eyeing the release of March US jobs data  later in the global trading day. Reaction to the Bank of Japan's tankan survey of business sentiment released before the market opened was limited, with attention instead on  Monday's report detailing responses gathered after the quake.

The post-quake results, "are expected to be severe," said Tsuyoshi Segawa,  equity strategist at Mizuho Securities. Beleaguered Tokyo Electric Power was down 9.65 percent at 421 yen, the  company now having lost around 80 percent of its pre-crisis market value. Moody's ratings agency on Thursday downgraded the company by three notches citing the "significant financial obligations" faced by TEPCO due to damaged  facilities and possible compensation liabilities. Local media reported Friday that the Japanese government is considering injecting public funds into TEPCO as it faces mounting damage costs and possible compensation payments, but not to the level of nationalising it.

Three weeks on from the March 11 earthquake and tsunami, the situation at  Fukushima Daiichi remains unresolved after the plant's reactor cooling systems were knocked out, triggering explosions and fires and releasing radiation. Radiation from the plant northeast of Tokyo has wafted into the air, contaminating farm produce and drinking water, and seeped into the Pacific Ocean, although officials stress there is no imminent health threat.