@neosovereign
Waaay late to the party, but
Makoto describes the size of the barrier as
It made me think of the Tokyo Dome, but I thought it might've actually been even bigger
The Tokyo Dome is 62 meters tall. But, Zagan is described as
he was probably over a hundred meters tall, which made dragons and giants look like kittens
Zagan is described as a lion, so presumably a quadruped, longer than he is tall. Thus, he must be significantly bigger than the entirety of the barrier.
He would have had to attack from the outside. The barrier absorbs mana attacks, but Zagan seemed to mainly use melee attacks with his body. So, I guess him attacking Sakurai would've taken the form of swiping blindly into the barrier hoping to hit him. Like a very big kitten playing with a very big ball.