Spinel Sun is the cat-like magical guardian that Eriol Hiiragizawa created to match Clow Reed's Cerberus. His true form is a winged black panther, though he usually appears as a small winged cat. Ruby Moon calls him "Suppi" and is always on his case about being too serious—he'd rather spend time reading and keeping to himself than actually having fun. For most of the series, he stays hidden from the main cast, which works out when he accidentally crosses paths with Cerberus in his smaller form. Cerberus has no idea who he really is and just assumes he's some kind of monster, so naturally he starts feeding him sweets. The plan backfires spectacularly: the sugar turns Spinel Sun into a hyperactive mess that can't stop eating. It's not until right before the final showdown that Cerberus figures out what's actually going on. When they finally face each other for real, Spinel Sun seems to be winning at first, but Cerberus's determination to protect Sakura proves stronger. In the end, he's the one who comes out on top.
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