Gamba Osaka striker Patric said he was racially abused on Twitter following their 3-1 extra time win over Urawa Red Diamonds in the J-League semi-final playoff on Saturday.
The Brazilian, who joined Gamba last year having first played in Japan for Kawasaki Frontale in 2013, scored the third goal at the Reds' Saitama Stadium to send the holders through to the two legged final against Sanfrecce Hiroshima this week.
The 28-year-old said he was shocked by the abuse.
"There were really disappointing and cruel, racially abusive posts. Anyone would be hurt by these," he posted on Twitter.
"I'm really proud to be black. My son is black and we are really happy. Only God knows how sad I am with this case.
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"This is the first time I've faced racial discrimination and I never dreamt of being on the receiving end in this country. I really like and respect this country. For me this is the most well-mannered and cultured country in the world.
"I hope the matter will be properly dealt with. To the person who has posted this, you should not do these things as a human being."
Gamba were critical of the abuse, while Kyodo News reported the J-League said it would "continue working to stamp out racism."
"It is extremely regrettable that this kind of thing is happening at a time when Gamba Osaka is trying to educate human rights issues on a daily basis," Kyodo quoted the club as saying on Sunday.
"Gamba Osaka will not under any circumstances tolerate racist behaviour."
