The details of what happened to a Tokyo couple whose bodies were burned in Tochigi Prefecture are starting to become clearer following the arrest on Monday of their daughter’s common-law husband, the suspected mastermind, according to police sources.

So far, six people have been arrested in connection with the murder of Ryutaro Takarajima, a 55-year-old business owner, and his wife, Sachiko, 56, who were found dead in mid-April.

A joint investigation team consisting of the Metropolitan Police Department and the Tochigi Prefectural Police suspect that Seiha Sekine, the 32-year-old husband of the couple's eldest daughter, orchestrated the murder and conspired with five other suspects.