Yanai's net worth rose $5.6 billion to $24.9 billion, propelling him to the top for the first time since 2016. The gains were mainly thanks to the rise in the value of Fast Retailing, the world's third-largest clothing retailer, in which Yanai and his family own a 44% stake.
Known as a leading voice in corporate Japan, Yanai recent made headlines by raising first-year salaries for new hires by around 20%.
Yanai placed 41st on the world's richest list. In Asia, he ranks behind Tencent Holdings Chairman Pony Ma Huateng, who came in 20th with a net worth of $38.8 billion.
Son fell to second place after his net worth increased at a slower clip, rising $2.1 billion to $24 billion. The gains were due to the rise in SoftBank Group's shares. The maverick investor is making huge bets on global technology companies through the nearly $100 billion SoftBank Vision Fund.
Ranked third was Takemitsu Takizaki, the low-profile founder of Osaka-based sensors giant Keyence, whose net worth rose by $1 billion to $18.6 billion.
The top three bucked the overall trend among Japan's 50 richest, whose collective wealth fell from $186 billion a year before to $178 billion.
The top 10 in the 2019 edition of the list are all men. The country's first self-made female billionaire, Yoshiko Shinohara, dropped off the list after shares in her temporary staffing company Persol Holdings lost more than a third of its value in the past year.