TOKYO — When the Top League competition was formed in Japan in 2003, few people would have imagined that 10 years later it would have lured players the caliber of Sonny Bill Williams, Ma’a Nonu, Jerome Kaino, George Smith, George Gregan and Fourie du Preez.

Japan is a second-tier rugby nation, and the sport sits well behind soccer and baseball in popularity, but the Top League has punched above its weight in attracting stars to its teams despite being weaker than Super Rugby or the top European competitions.

The reason is simple: money. Some players, like Williams and Smith, have earned more than 1 million New Zealand dollars, or about $835,000 a season. Foreign players of all different standards have all been able to earn far more in the Top League than they would have earned in their home countries, and they also get to play a shorter season at a level that is not as physically demanding as what they face back home.

The Top League teams have been able to pay for those players because each is owned by a big corporation, and they are willing to shell out top dollar in the hope it will bring their team success and glory. Suntory, Panasonic, Toshiba, Ricoh, Kobe, Yamaha, NTT Communications, NTT Docomo, Kintetsu, NEC, Canon, Toyota (two teams), Coca-Cola, Kubota and Kyushu Electric own the teams that make up this season’s Top League.