A group who claimed to have taken Kenji Goto hostage sent about 10 e-mails to his wife from late November to early January, demanding ransom, according to government sources.
The group, which is believed to be the Islamic State, demanded 2 billion yen in ransom in the e-mails. However, later during Prime Minister Shinzo Abe's tour of the Middle East, the group raised the ransom by about 10 times what it initially demanded.
Under such circumstances, the government believes there was a change within the group regarding the negotiations over the Japanese hostages. The government is continuing to gather information.
A member of the group first e-mailed Goto's wife in late November, according to the sources. She noticed the existence of the e-mail in December and opened it to read the English message, which claimed the group had detained Goto. The wife then contacted the government.
Later, the wife replied to the sender, and by early January, the group had sent her about 10 messages, demanding about 15 million euro, or about 2 billion yen, in ransom.
The e-mail messages contained some information that only Goto knows, and the sender's e-mail address was the same as that used in sending messages in other cases in which foreigners were taken hostage by the Islamic State.
In light of these facts, the government concluded it was highly likely that Goto was taken hostage.
In the video the captors released on Tuesday, a member of the group threatened to kill Goto and Haruna Yukawa unless the captors receive $200 million (about 23.6 billion yen) in ransom.
This is about 10 times more than what they initially demanded from Goto's wife, and they also changed the currency of the demand from euros to dollars.