The freed OSCE observers have arrived in Kiev after being held for more than a week.
More top news
Satoshi Uematsu, 26, was sent to the Yokohama District Public Prosecutors Office in Kanagawa prefecture.
West Yorkshire Police confirmed a 32-year-old woman was taken into custody in connection with the alleged threats.
Five women shared their views about whether Hillary Clinton's Democratic presidential nomination is a defining moment in US history.