Yokozuna Asashoryu, who announced his retirement Thursday, is one of the strongest sumo wrestlers of modern times.

But his frequent misbehavior — long overlooked by the Japan Sumo Association — also made him one of the most controversial grand champions of all time, critics said.

"It's not only Asashoryu's problem. The root of the problem is the association's economic motive," said journalist Yorimasa Takeda, who accused Asashoryu of match-fixing in an article published in a weekly magazine in 2007.