Complex sentence: Mitsuru, unlike the rest of the Moonlight Bandits, had been raised by humans, so he has no idea what his clan's weaknesses are and is not used to his transformation.
Split into simpler sentences: Mitsuru, unlike the rest of the Moonlight Bandits, had been raised by humans. Because he grew up with humans, he has no idea what his clan's weaknesses are and is not used to his transformation.