[9][10][11] Originally intended to be a human, Sakai was inspired to anthropomorphize the character after doodling a rabbit with its ears bound in a style reminiscent of a samurai topknot.

Eventually the trio went their separate ways when the boys were sent to be trained as samurai in the Dogora school of Bujitsu (en: arts of war).

However, on the trip there the boys witnessed a confrontation where a gang of arrogant Dogora students attacked a lone traveler named Katsuichi.

Katsuichi initially refused, but relented when Usagi stood outside his home day and night through unpleasant weather long enough to convince the teacher of his determination.

For years, Usagi was the exclusive student of Katsuichi-sensei, and although he proved a mischievous pupil who got into various misadventures, he also excelled at his studies to become a formidable warrior.

The region's daimyō, Lord Mifune, was observing the contest and was impressed with Usagi's skill enough to offer him a position as a retainer.

Kenichi decided to stay, and would eventually become headman upon Usagi's father's death, which comforted Mariko somewhat against the loss of her other dearest friend.

That war concluded at the battle of Adachigahara, sometimes referenced as Adachi Plain, where Mifune had the upper hand until Buichi Toda, one of his subordinate commanders, betrayed him and joined with Hikiji.

In the course of his "warrior pilgrimage", he made deep friendships with many, including the young Lord Noriyuki of the Geishu Clan and his valiant bodyguard Ame Tomoe, the cynical rhino bounty-hunter Murakami Gennosuke, the enigmatic demon hunter magic swordsman Sasuké the Demon Queller, the brilliantly astute Hidden Christian Inspector Ishida, the renegade cat kunoichi Chizu, and the sly street-entertainer/petty thief Kitsune with her apprentice Kiyoko.

A rabbit rōnin named Yukichi Yamamoto, Usagi's cousin, who now walks the Warrior's Pilgrimage in search of harmony as well.

[12][13] Usagi appears in two episodes of the 1987 Teenage Mutant Ninja Turtles animated series, voiced by Townsend Coleman.

A short pilot episode for an animated television series, Space Usagi, was created but cancelled following the failure of Bucky O'Hare and the Toad Wars.

Usagi makes his debut in the second season of the 2003 Teenage Mutant Ninja Turtles series, voiced by Jason Griffith.

Usagi went on to make several other appearances, including as Leonardo's guide when the turtle was accidentally sent to his world, and as an attendant of the wedding between April O'Neil and Casey Jones.

In his home dimension (presumably an alternate reality of Feudal Japan), Usagi clashes with his archenemy, the wolf-demon Jei, who escapes from him yet again.

While setting camp, Usagi is ambushed by the Ninja Turtles who are controlled by Jei's evil magic, after brought from his dimension.

After defeating to white ninjas, Usagi, the Turtles and Kintaro to reach the Temple Palace, until they discover that Jei was waiting for them.

Usagi has appeared as a playable character in Teenage Mutant Ninja Turtles: Shredder's Revenge in the Dimension Shellshock downloadable content.

Wizard magazine rated him as the 57th greatest comic book character,[16] while Empire rated him as the 31st greatest comic book character, stating that the noble leporine's longevity can be put down to an intriguing mix of historical and cinematic influence, cute fluffy bunnyness, and an ability to slice and dice with stunning efficiency.