JYJ Fan Club: March 1 to 6 (until 11:59 pm)
Official Pre-sale: March 1 to 10 (until 11:59 pm)
E-Plus*: March 12 (6 pm to 11:59 pm)
General Sale: March 15 (start at 10 am)
You will know the seat numbers when you exchange your 'admission vouchers' on the day of the concert. Seating is determined by the lottery.
Note: if you are not familiar with how ticketing in Japan goes, the official fanclub usually has priority to apply for tickets. If there are tickets left, then they will do a public sale.
*E plus is a ticketing agency.
Ticket price is 10,500 JPY wherever you may be seated.
I can't access JYJ Japan right now but will translate the details as soon as I can.