The factual story for Rilakkuma's being is that he mysteriously appears in the female office worker Kaoru's apartment one day. He is a soft toy bear who has apparently decided to take up residence there. On his back is a zipper which when opened reveals a light blue polka dot patterned material. The reason for the zipper on his back is unknown.
He was first seen in a series of picture books called Rilakkuma Seikatsu produced by San-X but since has become equally popular as a soft-toy character. In the picture books, he is often seen dressed up in a variety of costumes such as a kappa costume. In addition, it is implied that even in his usual appearance, his entire lower body is a costume, which he will often replace when it gets old or dirty (Rilakkuma is frequently seen sitting around waiting for suits that look exactly like him to dry on the clothes line). However, it is not clear whether his head is also part of his costume.
His favorite foods are dango, pancakes, omurice, custard pudding, and grapes. True to his name, he enjoys relaxing and his favorite things include sleeping, lying around, watching television, listening to music and soaking in hot springs. He loves using Kaoru's yellow bean bag pillow, although there has been some controversy whether or not the yellow bean bag pillow is in fact Kiiroitori.
Korilakkuma and Kiiroitori
Rilakkuma is often accompanied by Korilakkuma "a mysterious white bear cub" . Kiiroitori fictionally named her Korilakkuma because she looks like little Rilakkuma ("ko" means a little child in Japanese.). She also mysteriously appeared at Kaoru’s house. She is full of vigor and is very mischievous.
Kiiroitori is a yellow chick who lives at Kaoru’s house. Kiiroitori means “yellow bird” in Japanese. He used to be in a birdcage but now he comes out at his own discretion and scolds Rilakkuma and Korilakkuma because Rilakkuma is too lazy and Korilakkuma is too mischievous. Sometimes he feels down because he thinks he scolds them too much. He plays a tsukkomi role (considered to be the smarter, more logical one who criticizes others for making mistakes). His favorite thing is to save money (such as the loose change found while cleaning). Kiiroitori is basically the opposite of Rilakkuma because of the bird's hard-working nature and love of cleaning. Kiiroitori is Kaoru's pet chick. Korilakkuma frequently plays pranks on Rilakkuma while he is sleeping, such as drawing on him, putting headphones on him and sewing odd color patches on his bear suits. Most of the time, Korilakkuma does not speak, but occasionally she knows what Rilakkuma is saying.
Korilakkuma also has the appearance of a bear, but also has a red button attached to her chest, and so it seems that she is also not a real bear. However, unlike Rilakkuma, she doesn't have a zipper on her back. Her favorite foods are strawberries, apples and cherries and she loves playing with her radio controlled duck. Like Rilakkuma, she also likes listening to music, particularly at loud volumes using her music player. Though she dances excitedly, she is usually listening to piano or pop music.
Rilakkuma and Tarepanda, another San-X character, have been described as "huge hits in Japan" by The New York Times. As of May 2010, Rilakkuma ranked as the fifth most popular character in Japan in a survey of the Character Databank.
The San-X company puts staff members under obligation to create one cute character per month. Aki Kondo (also the creator of Okutan to Dannachan) saw a TV show about dogs. She wished to own a pet because at that time she was very busy working and hoped for a more relaxing life. Rilakkuma is an embodiment of her wish.
Between August 2, 2013 and September 16, 2013, the San-X Company collaborated with ENJOY!BASEMENT DINING to create a Rilakkuma-themed cafe in Harajuku. 
- Rilakkuma Seikatsu - Daradara Mainichi no Susume (Aki Kondou, March 2004)
- Dararan Biyori - Rilakkuma Seikatsu 2 (Aki Kondou, November 2004)
- Tori Dayori - Rilakkuma Seikatsu 3 (Aki Kondou, May 2005)
- Kuma Goyomi - Rilakkuma Seikatsu 4 (Aki Kondou, September 2006)
- Utatane Kibun - Rilakkuma Seikatsu 5 (Aki Kondou, September 2007)
- Bonyari Kinenbi - Rilakkuma Seikatsu 6 (Aki Kondou, August 2008)
- Yanwari Jozu - Rilakkuma Seikatsu 7 (Aki Kondou, October 2010)
- Rilakkuma Daradara Shiiru Bukku (Aki Kondou, November 2004)
- Rilakkuma Dara Pika Shiiru Bukku (Aki Kondou, May 2005)
- Rilakkuma Gorogoro Shiiru Bukku (Aki Kondou, September 2006)
- Rilakkuma Howa Pika Shiiru Bukku (Aki Kondou, September 2007)
- Rilakkuma Nohohon Shiiru Bukku (Aki Kondou, August 2008)
- Rilakkuma na Mainichi (Rocket Company, Game Boy Advance, April 2005)
- Rilakkuma ~Ojamashitemasu 2 Shuukan~ (Interchannel, PlayStation 2, September 2005)
- Watashi no Rilakkuma (Rocket Company, Nintendo DS, April 2007)
- Chokkan Asonde Rilakkuma (Smilesoft, Nintendo DS, September 2008)
- Rilakkuma Minna de Goyururi Seikatsu (MTO, Nintendo Wii, March 2009)
- Norinori Rilakkuma Hit Song Ongaku (Smilesoft, Nintendo DS, December 2010)
- Sutekina Okusan Magazine January 2009
- Tabuchi, Hiroko (May 14, 2010). "In Search of Adorable, as Hello Kitty Gets Closer to Goodbye". NYTimes.com.
- Interview with Aki Kondo (in Japanese) . November 11, 2006.
- "Bandai Rilakkuma netbook suffers from serious supercutitis", Engadget, July 13, 2009. Retrieved July 24, 2009.
- "You Will Die of Cute Overdose! Rilakkuma Cafe Opens for Limited Time". Retrieved November 29, 2013.