Former sumo grand champion Harumafuji has been fined 500,000 yen (£3,280; $4,400) in Japan after being found guilty of assault.
The 33-year-old wrestler from Mongolia admitted hitting a junior wrestler over the head with a karaoke machine remote control during a night out in Tottori in October.
He has already apologised and stepped down over the incident.
The case rocked the world of sumo, a hugely popular ceremonial sport.
The assault on fellow Mongolian Takanoiwa happened while they were out drinking with other wrestlers in a bar in the western city.
The grand champion is reported to have been angered that his countryman was checking his phone while being given advice, seeing it as showing a lack of respect.
The latter was admitted to hospital with concussion and a fractured skull.
Two others involved in the incident have faced disciplinary action and Takanoiwa’s stablemaster – as coaches are known – has been demoted for allegedly delaying reporting the incident.
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Harumafuji started his career in Japan at the age of 16 and was promoted to grand champion or yokozuna – sumo’s highest rank – in 2012.
He released a statement in late December, Reuters news agency reports, saying his life “is now set to be sharply different from what I thought it would be”.
“I have a feeling of chagrin, to be honest. But the responsibility is all mine.”
What is sumo?
- Japan’s much-loved traditional sport dates back hundreds of years
- Two wrestlers face off in an elevated circular ring and try to push each other to the ground or out of the ring
- There are six tournaments each year in which each wrestler fights 15 bouts
- Wrestlers, who traditionally go by one fighting name, are ranked and the ultimate goal is to become a yokozuna (grand champion)
How does sumo wrestling work?
What other scandals clouded the sport recently?
- Last year, a wrestler and his coach had to pay nearly $300,000 to a fellow fighter whom they had allegedly abused so badly he lost sight in one eye, according to reports
- Several wrestlers have been implicated in match-fixing scandals and links between sumo and the mafia-like yakuza crime syndicates
- Another Mongolian grand champion retired from the sport in 2010 after reports of his involvement in a drunken brawl
- In 2007 a sumo stablemaster received six years in prison after a novice was beaten to death by older wrestlers