In the incident on Wednesday, Takashi Kawamura pulled down his mask and put Goto's gold medal between his teeth as he stood in front of a backdrop used for press briefing that urges people to wash their hands and socially distance to prevent Covid-19 infections.
Trending posts on Twitter said Kawamura had turned Goto's gold medal into a germ medal, which in Japanese is pronounced the same. Some called for Goto to get a replacement for the medal she won at the Tokyo 2020 Games playing for Japan.
Biting down on medals, which only contain a small amount of gold even if gold, is common among athletes and even prompted a humorous tweet from the official Tokyo2020 account to confirm that " medals are not edible."
"It is unfortunate that he was unable to feel admiration and respect for the athlete," Toyota said in a statement on Thursday about Kawamura. "And it is extremely regrettable that he was unable to give consideration to infection prevention," said the world's biggest car maker.
Toyota, which owns the Red Terriers softball team that Goto plays for, dominates the economy of the region in central Japan where the city is located.
"I forgot my position as Nagoya mayor and acted in an extremely inappropriate way. I am fully aware that I should reflect on that," Kawamura said in a televised apology after Toyota released its statement.
His apparent disregard for coronavirus etiquette in a country where mask wearing is common, even in stifling summer heat, comes as Covid-19 cases spike in Japan as the more infectious Delta variant spreads.
Kawamura, who has courted controversy before for trying to shut down an exhibition on women forced to work in Japanese army brothels during World War Two, was re-elected in April for a fourth term.