- Jewel: Euclase
- Species: Beagle
- Gender: Male
- Jewel Power: Intellect and Vision
- Attribute: Magical Blue
- Voiced by: Hitomi Yoshida
Yuku is a Jewelpet detective. He's a brown and white Beagle who symbolizes intellect and vision and wears a blue beret and a light blue bow tie. He first appeared in Episode 17 when Rinko and her friends discovered his Jewel Charm inside the Prime Minister's office. After he was awakened, he somehow didn't like to help Rinko until they convinced him. He is a hardworking person and sometimes prideful, but his detective study in the Magic Academy is impressive, even though he has an Acrylic Class ranking in his magic. He always doesn't rely in magic on solving things, in fact, he hates on using his Jewel Eyes. Instead, he uses his intelligence to study things and came out with a theory, which sometimes emits a powerful aura from his body. He appears on Jewelpet Twinkle on Jewel Grand Prix along with his partner Gunho and they lost by Akari and Ruby. He appears again on Jewelpet Sunshine on episode 26, Ruby notices him when he drawing and Yuku has a crush on her and want to marry her, Ruby know he use her a model and Ruby accept to his model. His birthday is on November 3 and his name is based on the mineral Euclase.