Complex sentence: When he saw the Evil Spirit trying to harm his childhood friend, Yuki, his Banishing Shift went out of control, causing a great crater to form, vaporizing the bodies of those slain except Yuki, and also cleansing the area of the evil spirit.
Split into simpler sentences: When he saw the Evil Spirit trying to harm his childhood friend, Yuki, his banishing Shift went out of control. He caused a great crater to form, wiping out all his friends except Yuki and cleansing the area of the evil spirit.