Yuku is a naturally colored beagle, usually in Light Brown, Brown and White in color alongside his blue Jewel Eyes. He only wears a Beret on top of his head and a light blue ribbon on his neck.

In the first series, Yuku believes magic shouldn't be relied on for everything, based on his own lack of talent at it.

As the Jewelpet of Intellect, Yuku is one of the more intelligent Jewelpets and has better deductive capacities than any other.

In Jewelpet, he's the Jewelpet partner of the Prime Minister, awoken by him, Rinko and her friends.

In Jewelpet Twinkle☆, he's the partner of Gunho, a contestant at the Jewel Star Grand Prix from the same school as the Three Angels. They fight and lose against Akari and Ruby.

In Jewelpet Sunshine, he's a painter who meets Ruby at a group date and asks her to pretend to marry him to please his grandparents. Ruby gets angry at him for lying to them and he ends up genuinely falling in love with her. He's later seen in the human world trying to sell his art.

In Jewelpet Kira Deco, he's one of the ninjas in the Japanese-styled palace.

In Jewelpet Happiness, he's searching for a girl who helped him many years ago. That girl turns out to be Taira.

In Lady Jewelpet, he's one of the dogs used to test the Petit Ladies' skill at dog-walking. He is partnered with Charon for being the gentlest and most perceptive.

(Source: Jewelpet Wikia)