Nicola Furlong, 21, was found dead in a Tokyo hotel room, police said.
Tokyo (written by Kyung Lah/CNN) -- Japanese authorities are holding an American man on suspicion of killing a female Irish exchange student in Tokyo, a police spokesman said Friday.
Police charged a second American man with groping the dead woman's friend.
Nicola Furlong, 21, died in a hotel room in the presence of one of the men last month, according to the Tokyo Metropolitan Police.
The 19-year-old man, whom police declined to identify because he's considered a minor under Japanese law, was arrested on suspicion of murder, a spokesman for the Tokyo police said Friday.
The man, a musician, had been previously detained on suspicion of improperly touching Furlong's friend, but was not charged with that offense. The police have 20 days to decide whether to charge him with murder.
The other American man, James Blackston, 23, has been charged with groping the friend, said Tsutomu Nakamura, his lawyer.
Blackston, a dancer from the Los Angeles area, faces up to 10 years in prison if he is convicted. His lawyer said he is not guilty and will fight the charges.
He is alleged to have improperly touched the woman during a taxi ride with Furlong and the 19-year-old man to the hotel where the victim died.
Authorities have not said how the four ended up together, but Japanese media have reported that the women were attending a Nicki Minaj concert in Tokyo when they met the men and decided to accompany them to their hotel rooms.
The hotel staff went to the room after customers complained of loud noises coming from it, police said.
When the staff entered the room, they found Furlong unconscious in the company of the 19-year-old and called the fire department, according to authorities.
The death is believed to be a result of suffocation by cervical compression, the police said.
Furlong's parish priest, the Rev. Jim Fitzpatrick, described her last month as an "outgoing, bubbly sort of girl and very well liked." He said she had been looking forward to coming home after being in Japan since October.
Everyone in Furlong's close-knit rural community, which has only 300 or 400 families, was devastated by the news of her death, according to the priest.
"When the death of a young person happens, everybody knows and is in some way involved or concerned," Fitzpatrick said. "When it happens in tragic circumstances and so far away from home, it has a double impact on people."
Her parents last spoke to her the day she died, he said.