Complex sentence: The series treats these characters very differently than do the fans--they are considered a group of three, with Saturn excluded due to her unique role in the story, however, Saturn does join them later in the series after the third arc.
Split into simpler sentences: The series treats these characters very differently than do the fans--they are considered a group of three, with Saturn excluded due to her unique role in the story. However Saturn does join them later in the series after the third arc.