Layout of a block of seats. The block numbers indicate the tier. 100s for the 1st tier (expensive seats), 200s, for the 2nd tie, and 300s here for the 3rd tier (cheap seats, ¥5000 for this event).

Here, you should check your seat No.
If your seat No. is 111 to 124, enter on the left side of the block. If it's 125 to 138, go to the other corridor entrance on the right side of the block. The field is toward the top of this diagram (Row 1).