Although Cairo was a bit taken aback, he still has the experience of the Reviving King and his arm moved in its own to place his staff in front of him
However, the sword slash composed of chaotic colored lights actually vanishes in front of him before he felt it appear behind him
Despite the attack targeting him from behind, Cairo still managed to use space magic to lock the space around him. Del has a natural talent for space magic and his practical skill over it was higher than Cairo's thus, despite locking the space, that dimensional slash will still destroy Cairo's defense
That was already enough though, the dimensional slash needs a bit of time to destroy Cairo's defense and he uses that time to fly away
Too bad that a Del being serious in a fight is a real headache as he is a space mage