Spinel Sun is a cat-like magical guardian created by Eriol Hiiragizawa as a counterpart to Clow Reed's original guardian, Cerberus. In his true form, Spinel Sun is a winged black panther, while his false form resembles a small winged cat. Ruby Moon affectionately calls him Suppi. He usually spends his time reading and maintains a calm demeanor. Ruby Moon often teases him for needing more fun.
Throughout the series, Spinel Sun mostly stays out of sight from the main characters. However, he once encounters Cerberus in his false form. Fortunately, Cerberus doesn't suspect anything and instead declares him a monster, feeding him sweets. Unbeknownst to Cerberus, these sweets turn Spinel Sun into a hyperactive eating machine. Cerberus only discovers Spinel Sun's true identity just before the final battle, where the two cats confront each other.
Initially, it seems that Spinel Sun has the upper hand in their fight. However, Cerberus' greater determination to protect Sakura allows him to ultimately defeat Spinel Sun.
