Complex sentence: But Guan Yu, unlike Lü Bu, is extremely loyal to his master, Liu Bei, whom he believes is the rightful ruler of China, and refuses to be swayed to Cao Cao's side.
Split into simpler sentences: But Guan Yu, unlike Lü Bu, is extremely loyal to his master, Liu Bei, whom he believes is the rightful ruler of China. He refuses to be swayed to Cao Cao's side.