I think the logo should be shifted slightly into the (1,1) direction (45 degrees), i.e. up and to the right. The bounding box may be centred perfectly, but the character inside the circle looks lopsided.
Edit.
It should be a bit more subtle than this, but the circle being 40x40 pixels (the あ being 22x22), a shift of one pixel up and one pixel to the right (or one pixel up) already looks better (to me):