This is written on the largest forum in Japan,"Channel-2".
Whether this is true or not, most Japanese doubt the abduction.
questionable points of this abduction
#the responsibility claim has NO religious rhetoric,or expressions like "Al-Qaeda"
#the claim is dated by A.D., not Islamic calendar(though 4/11,the deadline date, is the significant day for Shiite, Islamic calendar is not used. Why?)
#the claim is dated by Japanese way(year/month/day)
#the video camera used for the film is made in Japan(It's a SONY!)
#According to aljazeera, the terrorists are strange to them.
I can't translate anymore because of my poor English ability.
You should check it out.
http://news10.2ch.net/news5plus/