Around half of the money will be targeted at infrastructure development, with Tokyo seeking to match its desire to export transport systems and power grids with the gaping needs of the continent.
Japan's overseas development aid "will be about 1.4 trillion yen (USD 14 billion)" Prime Minister Shinzo Abe said at the start of a three-day conference in Tokyo involving the leaders of more then 40 African countries.
Japanese firms are keen to develop their presence in Africa's growing market, and the country as a whole needs access to the resources the continent harbours.
Despite relatively long-standing connections, Japan's importance to Africa has slipped behind that of China, whose more aggressive approach has given it five times the trading volume and eight times the direct investment.
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The five-yearly Tokyo International Conference on African Development (TICAD), a get-together of political leaders from across Africa, is Japan's two decade old effort to boost links.
That theme was taken up by Abe.
"What Africa needs now is private-sector investment. 'PPP', or 'public-private partnership', leverages that investment," Abe told delegates.
Tokyo's commitment to Africa differed from that of other nations, Abe said, in remarks that appeared to have been a reference to China.
Beijing is criticised in some corners for what is sometimes seen as prosecuting little more than a resources grab and for not linking investment with demands for improved human rights or more transparent governance in recipient countries.
The focus on shifting the relationship was welcomed by delegates, with South African President Jacob Zuma saying the continent's economy had to develop.
"Africa must move from a path driven by commodities export to one led by industrialisation and diversification," he said.
"Three points are crucial (in the path to development): market integration, industrial development and infrastructure development."
Ismael Omar Guelleh, the president of Djibouti, said the dearth of roads and ports across Africa was costing it two percent growth each year.
At the same time, Japan's firms see Africa as an opportunity for expansion at a time that their home market is contracting and stultifying because of a population that is rapidly ageing and is forecast to shrink.