[Hatix]

Well, Yokohama Arena has little different seating chart (it's just differently named). You've basically got 2 types of seats: Center seats and Arena seats. Center seats are in the center (duh), Arena seats are on the side.
The center is has 12 blocks: 4 rows (A-D) with each 3 columns (1-3).
But this is where the confusion comes: the arena seats (on the side) are also numbered with blocks starting from A-F (with each more than 3 blocks).
The seating plan for the arena seats can be seen on the site of Yokohama Arena, but the center seats is specific and is not on their site.
I have figured out the block pattern for the center seats by seeing what is on all the tickets. And how to see that it's a center seat or an arena seat: above the block number, there is a text in katakana: center = センター and arena = アリーナ.
I have heard that in Yoyogi the center seats are called arena seats, which gives more confusion. But I don't think I'm very wrong, because the center A-block seats were very expensive, and the arena A-block seats were not very expensive, so that is another proof.