The storm was about 160km northwest of Kume Island in Okinawa on Saturday, moving northwest at 15km/h, the Japan Meteorological Agency said.
Five elderly people suffered non-life-threatening injuries, with three falling due to the wind, the Okinawan prefectural government said.
Domestic airlines, ANA and Japan Airlines, cancelled flights to the region.
The typhoon has maximum sustained winds of 162km/h, with gusts reaching 216km/h.
Okinawa and Amami island in Kagoshima prefecture are the main areas expected to be affected in Japan.
The China National Meteorological Centre said Typhoon Dolphin was expected to cross China's eastern and southern coast between late Sunday and early Monday, most likely between Zhoushan city in Zhejiang province and Fuding city in Fujian province.
It is expected to bring winds of 38-45 metres per second near its centre.
Rain and strong winds are expected to affect eastern China through August 12, including parts of Shanghai and neighbouring provinces.
Some areas of eastern Zhejiang could receive more than 600mm of rain, according to forecasters.
Zhejiang raised its coastal typhoon alert to its highest level, halted port operations and suspended 162 passenger ferry routes.
Ningbo Lishe International Airport in Zhejiang said it would halt operations late on Saturday and suspend all flights on Sunday.
Shanghai's Yangshan port had been cleared of vessels by late Friday, while some rail services in the Yangtze River Delta will be suspended from Sunday.
In Taiwan, 63 international flights were cancelled because of the typhoon, the government said.
Heavy rain was expected in northern parts of the island at the weekend, though authorities had not ordered evacuations as of Saturday.
China has ordered that, due to the typhoon, ships passing through the Taiwan Strait must heed its traffic control instructions - measures that Taipei denounced as "ridiculous", saying that Beijing has no right to restrict access to international waters.
China, which views democratically governed Taiwan as its own territory, also claims the strategic strait.
Both Taipei and Washington reject that claim.
