According to a May 2010 survey, Rilakkuma was the fifth most popular cartoon character in Japan. In a popularity poll in May 2021, Rilakkuma was ranked number one among San-X characters!

Rilakkuma™ is a Japanese cartoon character whose true identity is unknown; it has a zipper on its back, revealing a fabric with a polka dot pattern inside. The covers of the picture book series are decorated with a partially open zipper and polka dots. In the picture books, Rilakkuma is occasionally seen wearing other costumes, such as a kappa or a rabbit, besides the bear costume. The bear costume is purchased, and there are many spares, which are sometimes washed and dried. It has also shrunk and become old, and has been pranked by Korilakkuma with added decorations. However, it is uncertain whether its head is part of the costume, or if there are spares or if it is ever washed. Its ears sometimes get flattened from sleeping, and it seems to be able to move them freely.

A bear mascot suddenly appeared in the home of office lady Kaoru and has been accompanying her ever since. It's unclear who is inside the costume, and the bear doesn't do anything particularly useful, just lazes around all day. Rilakkuma's biggest concerns seem to be his daily meals and snacks. His favorite foods include dango, hotcakes, omurice, and pudding, and he dislikes overly spicy food. He often rolls around while lying down and loves his yellow cushion. His hobbies include watching TV, listening to music, and taking hot spring baths.

It is a cream-colored teddy bear with pink ears, paws, and a white belly. It has no zipper on its back and a red button on its chest, and a high body fat percentage. Like Rilakkuma, it suddenly appeared at Kaoru's house and was named Korilakkuma (meaning "Little Rilakkuma" in Japanese) by Kiiroitori. Rilakkuma once asked it, "Where did you come from, bear?", implying they didn't know each other. Korilakkuma often pulls Rilakkuma's ears and cheeks, and likes to prank Rilakkuma with Kiiroitori; it's a mischievous child. Korilakkuma's favorite foods are strawberries, apples, and cherries, and its hobby is listening to music.

This is Kiiroitori, a pet chick raised by Kaoru, who arrived at Kaoru's house even before Rilakkuma. Since Rilakkuma moved in, Kiiroitori has been able to enter and exit its cage on its own and proactively takes care of household chores such as cleaning, cooking, and sewing. It cleans up after the lazy Rilakkuma and mischievous Korilakkuma, constantly scolds the lazy Rilakkuma for wandering around, and is often teased by the playful Korilakkuma. Its hobby is saving money, and it collects any coins it finds while cleaning in a jar.

A true bear living in Honey Forest, with dark brown fur, dense white chest fur, yellow Rilakkuma paw prints, and fangs when its mouth is open. It is a new friend discovered by Shirokuma in Honey Forest and was named by Shirokuma. Chairoikoguma is slightly smaller than Shirokuma, loves honey, and smells sweet like honey, which is why a drop of honey in the shape of a bear's head is stuck to its bottom. Chairoikoguma likes to roar and walk on all fours. It plays with Shirokuma when she visits Honey Forest and shares honey with Shirokuma, Rilakkuma, Kiiroitori, and others.