The Rabbit of the Cursed Sohmas
Momiji was born two months premature to a German mother and a Japanese member of the Sohma family. Born as the rabbit of the Sohma family curse, Momiji can transform into a rabbit when embraced by a member of the opposite sex. Because of the curse, Momiji's mother found it difficult to connect with her son as she could not hug or hold him lest he turn into an animal. The stress of this dilemma eventually caused her to snap mentally as she would angrily lash out at Momiji whenever she seen him and she could not smile. Eventually, Momiji's mother would request for Hatori to erase her memories of her son as she could no longer put up with the stress of trying to raise him. To distance Momiji from the family, his father had him take up residence at the main Sohma house.
Momiji was created as one of the major characters in Natsuki Takaya's Fruits Basket manga series. He was made as a character for Studio Deen's 2001 animated adaptation of the series, being voiced by Ayaka Saito in Japanese and Kimberly Grant in English.
Momiji stands at '5'1" (155.8 cm) and weighs 104.7 pounds, having blonde hair and brown eyes. He is 15 years at the start of the series and known to wear childish, lacy and ruffly clothing. When going to the same high school as Tohru and the older Sohma, he would wear the girl's version of their school uniform with shorts. Momiji would eventually start wearing the male version of the school uniform later in the series. When he transforms, Momiji becomes a yellow-colored rabbit with red eyes.
Momiji outwardly displays a childish and carefree personality, though also has a somber and mature side to him that is reflective of the events he faced with his mother and not being able to openly confess his relation to younger sister Momo. Due to his mixed upbringing, Momiji is capable of speaking fluent German in the manga and will often mix in spoken German with his comments while addressing others in Japanese. He is quite attached to Tohru as such where he wanted to hug her during their early encounters with little regard for the consequences that would result from him transforming. His feelings for her develop into an unrequited love throughout the course of the series.
Tohru would first encounter Momiji at the office complex she works at doing custodial work, unaware that he was a Sohma and that his father was an executive at the facility. Not understanding the boy's spoken German and a kiss on the cheek from him led a flustered Tohru to flee from him during their first encounter.
Momiji and Tohru would later meet at the high school culture festival as Momiji tagged along with Hatori when he came to check on Yuki and Kyo. Tohru would come to learn of Momiji's connection to the Sohmas and he would cause a commotion when he transformed due to hugging Tohru. He would provide support to Tohru during her visit with Hatori at the main Sohma house due to her feeling intimidated and uneasy around him from learning he was responsible for erasing the memories of outsiders that learned of the family curse.
Throughout the series, Momiji would continue to interact with Tohru and eventually winded up going to the same school as her, Kyo and Yuki. During their trip to the Sohma summer house, he would try to protect Tohru from the wrath of Akito before being beaten up by her. Momiji would also come to interact with Momo as she started to grow curious about his connection to her and her family, as well as having been continually watching over him from her thoughts of him.
By later in the series, Momiji underwent a good deal of physical growth and his feelings for Tohru developed into romantic ones. However, he knew that Tohru was falling for Kyo and would avoid confessing to her. In spite of this, Momiji would advise Kyo that he should be committing himself to Tohru instead of being obligated to play the role of the outcast in the family curse.
Momiji's curse would be broken by later in the series, being the second Sohma member after Kureno to break free from it. Despite pleas from a desperate Akito to still be part of the cursed group, Momiji turns down them down in spite of knowing he could not reclaim the life he once had with his family as he sought to move on with his life instead.
While it is unclear what happens to Momiji at the end of the series, he was shown in the final chapter talking to Hatsuharu about wanting to find a cute girlfriend to show off to Kyo.