It seems like the guy writing these letters just wants any fan of Kuroko's basketball to suffer. Then again with them not confirming exactly what the letter was, there is a chance that it could just be some copy cat guy trying to ride the fear train.

id still like to attend this event!

:O

I have fond memories of the 2 Comiket I attended, including waiting outside in the queue from midnight to get in at the start. Would be a shame if they have to cancel it, though I can understand why they would. There's easily tens of thousands (if not hundreds of thousands) of people there each day, it'd be a disaster if something happened.