Japan's 40 wealthiest businesspeople are worth $89.9 billion, up $10.7 billion from last year. An impressive gain but one that masks an uneven year for the country's tycoons. Twenty people are richer than last year, including eight of the top 10, helped by the yen's double-digit gain against the U.S. dollar. Six added more than $1 billion apiece to their fortunes.

The biggest gainer was the country's new No. 1, the retired and now largely low-profile Nintendo chairman, Hiroshi Yamauchi, whose net worth soared $3 billion in the past year and has tripled since 2006, thanks mostly to booming sales of the Wii gaming device. Close behind him is last year's richest member on the list, property developer Akira Mori, who gained $2.2 billion but not enough to stay on top.

Three former billionaires return to the ranks. They are construction tycoon Katsumi Tada, who apparently received a bid from U.S. Aetos Capital and Akira Mori's company earlier this year for his Daito Trust Construction; Akira's brother Minoru, who is building Shanghai's biggest tower; and Kagemasa Kozuki, whose Konami gaming company makes videogames for Sony's (nyse: SNE - news - people ) PlayStation and Microsoft's (nasdaq: MSFT - news - people ) Xbox.

In Pictures: Japan's 40 Richest

Three newcomers debut, including the list's youngest member, Mixi's 32-year-old founder, Kenji Sahara. He is the first under-40 member of Japan's rich list since 2005, when former Internet entrepreneur Takafumi Horie last appeared on the list (he was later sentenced to jail for violating securities law).

Other newcomers are Yokyu Kanazawa and his brothers, who together own Sanyo Bussan, a $2 billion (sales) maker of pachinko machines; and steel-parts magnate Hiroyuki Inoue, who grabbed the last spot with a net worth of $715 million, $105 million more than last year's minimum. Inoue's company Yamato Kogyo, founded by his father, is a member of Forbes Asia's 2007 list of 200 Best Under a Billion companies.

On the gloomier side, six people from the 2007 list failed to make the cut, and 14 are poorer, mostly because of falling stocks (the Nikkei index is down 20% since then) and plunging profits at a number of rich-list-owned companies. Two dropouts were Toichi Takenaka, whose Takenaka construction company's consolidated profits fell by two-thirds for fiscal 2007 because of fewer orders and higher costs, and Kenshin Oshima, head of consumer loan outfit SFCG, whose market value was halved. Sega Sammy's Hajime Satomi just barely makes the list, as his company's stock also tanked.

Another factor that could hold the group back is the graying of Japan's richest citizens along with the country's population. By 2030, one-third of all Japanese will be over 65. The average age of the country's 40 wealthiest is 66. That makes the group quite a bit older than the youthful tycoons of China, India and even South Korea. Indeed nine octogenarians rank among the top 40, three more than two years ago.

Only three females qualify for this year's top 40: Hiroko Takei, who inherited her fortune from her late husband; Chizuko Matsui, whose husband turned her grandfather's brokerage firm into a leading online securities firm; and Keiko Erikawa, chairman emeritus of videogame developer Koei. Erikawa, the list's only self-made female, shares a $720 million fortune with her husband, who co-founded the company with her.

Unlike the Billionaires List, which tries to home in on individuals, Japan's top 40 includes such families as the Kinoshita brothers and Kanazawa and his brothers. For people with publicly traded fortunes, net worths were calculated using April 25 stock prices and exchange rates. For people with privately held fortunes, we estimated what companies would be worth if public.

In Pictures: Japan's 40 Richest

With additional reporting by Tim Kelly