Complex sentence: He has an uncanny resemblance to Shinichi, so much so that Shinichi's childhood friend Ran mistook Kaito for him, the only noticeable difference between their physical appearance being their haircuts.
Split into simpler sentences: He has an uncanny resemblance to Shinichi, so much so that Shinichi's childhood friend Ran mistook Kaito for him. The only noticeable differences between their physical appearance being their haircuts.