Yuzu met Raku when it was a stray cat, out on the street during a rainy day. Yuzu felt sorry for the yellow cat and gave it a biscuit to eat. Forming a sort of attachment to Yuzu, Raku tried to follow her home, but was hit and killed by a passing car. From then on, Raku's spirit haunted the Human World, as its attachment to Yuzu continued to bind it to the Human World.
Raku is a cat with short blonde fur, a white underbelly, and long ears and whiskers. Its eyes are bright green, almost emerald in coloring. It has the ability to transform into what seems like a large Chinese lion guardian with a fiery mane and headband.
Karakura Lion JetKarakura Lion Jet (カラクラ・ライオン・ジェット, karakura raion jetto; "Karakura Sonic Lion" in the English sub): Transformed, Raku exhibits impressive speed, strength, and can surround itself with fire. Its power is close to a ranked Shinigami Officer as it is easily able to single-handedly overpower a Huge Hollow.
Soul Society arc
Raku returns sometime later as a spirit with unusually high Reiatsu, attracting Hollows. When the Hollows endanger Yuzu, it transforms into a lion to protect her. Don Kanonji, who organizes the Karakura Superheroes in order to protect the area from Hollows, dubs it the "Karakura Lion Jet" upon first seeing it. He also claims it as the team's "hero mecha" (a common staple in Super Sentai-styled anime), despite it not being mechanical.
After the Hollow is defeated, Raku, having fulfilled its purpose, passes on. Nobody other than Yuzu knows that Raku is actually the "lion jet". Yuzu and her sister Karin Kurosaki compare Raku to their older brother, Ichigo Kurosaki.
- In both anime versions, Raku is named after a camel ("Raku" is japanese for "camel" and "Cammy" is short for camel). Because it is the same color as camelhair long johns, (Yuzu's "camel-colored underwear" in the English version).
all information on Raku came from http://bleach.wikia.com/wiki/Raku