On another thread (which I don't remember exactly which one) on here they said you should bring the email you got just in case, but they said it may not be needed and just an ID but still I'd bring the email or receipt (at sakuracon, the kumori booth gave receipts for pre reg) just in case. Also your title and queTion don't match. First you ask if you have to on day 0, then don't even bring that up in the thread. Anyway you don't HAVE to so it day 0. You can do it whatever say you get there. But you CAN on that day