WBO world super flyweight champion Kazuto Ioka has been disciplined, the Japan Boxing Commission said Friday, after tattoos on his left arm became visible during his successful second title defense on New Year's Eve.

The commission's ethics committee decided Thursday to issue a severe warning to Ioka and the chairman of his gym, Takuya Kiya.

Japan's Kazuto Ioka (L) throws a punch at compatriot Kosei Tanaka on the way to successfully defending his WBO super flyweight title in Tokyo on Dec. 31, 2020. (Kyodo) ==Kyodo

JBC rules prevent fighters from appearing in a "manner that will make spectators feel uncomfortable" and that includes the display of tattoos. The controversy was sparked when Ioka's tattoos became visible after the foundation he had applied to cover them up flaked off during the fight.

"We would like to consider the possibility of using a masking agent in such cases. We are not thinking of changing the rules at this time," said Tsuyoshi Yasukochi, the JBC's secretary general.