A 22-year-old former sumo disciple has sued his then-stablemaster and a retired wrestler over a recently revealed 2014 assault, seeking ¥30 million ($274,000) in damages, sources said Thursday.

The suit, made public only now, was filed by the man last March against the 24-year-old former wrestler, who had been convicted of the assault, and their stablemaster Kasugano — a key member of the Japan Sumo Association — claiming Kasugano failed to exercise appropriate oversight on the attacker. The victim, who sustained a broken jaw, is still struggling with effects on his sense of taste.

The incident came to light only recently, fueling speculation that Kasugano may have tried to cover it up. It marks another blow for the sport, which is still reeling from an assault scandal that led to the retirement in November of then-yokozuna Harumafuji.