The brother of a French woman who went missing in 2018 during a trip to a tourist spot north of Tokyo said Friday he believes she was likely a victim of a crime, despite police investigations that have failed to determine whether there was an accident or foul play.

"We want the investigation file to be handed to the (French) authorities," Damien Veron said at a news conference at the Foreign Correspondent's Club of Japan in Tokyo, as that should give the family information that has, so far, been difficult to access.

The missing woman, Tiphaine Veron, 41, was expected to spend two nights alone at a lodging house in Nikko, Tochigi Prefecture, from July 28, 2018. But she disappeared on the morning of the second day with her luggage and passport remaining at her accommodation.

Damien has traveled back and forth between Japan and France multiple times to conduct his own investigations, with his latest trip involving time spent in Nikko from mid-October.

He said he has identified some discrepancies in information he and the local police have discovered, such as in positioning data from her mobile phone.

He said he wants access to the findings of the Japanese authorities but finds it difficult to navigate the justice system to make that possible.

Despite the difficulties he has faced, Damien showed gratitude for the assistance he has received.

"I would also like to say we would have never been able to do all the search and investigations that we have done without the help of the Japanese people," he said.

"We are going to fight. Please don't forget Tiphaine."