The head of the Amon Clan has challenged you to a fight.

To those unfamiliar with the Yakuza/Like a Dragon series, the Amons are the secret superbosses of the games. They are extremely difficult and have absurd and bizarre fighting styles for the setting. In a series focusing on fist fights, the Amons use swords, guns, grenades, drones, rocket launchers, mimicry, magic, you name it. I wish you luck.

Also, while the Amon Clan had a rule forbidding men and women from fighting each other, it seems this rule has been abolished as of Infinite Wealth.