Police said it was a "completely unprovoked attack".
A 31-year-old Waikato painter and decorator was also charged and will be sentenced for indecent exposure in the Hamilton District Court on December 4.
A 35-year-old teacher from Papamoa, near Tauranga, will appear tomorrow in the Auckland District Court charged with assault with intent to injure.
The mother of one of the teens said her daughter and friend were travelling home on the train when they were confronted by five drunk men in costumes.
Police earlier said there was a large amount of public interest in this case and thanked the public for the information provided, Transdev and Auckland Transport for their support.