Hiro Soma
Hiro Sohma (草摩燈路 Sōma Hiro) is a fictional character in manga and anime entitled Fruits Basket, transforming into the ram of the Chinese Zodiac whenever he is hugged by the opposite gender or his body comes under a great deal of stress.
Hiro Sohma is the youngest of the cursed Sohmas. He is most commonly associated with Kisa Sohma as a companion. His mother became pregnant and had a baby girl named Hinata, so Hiro is now an older brother.
Personality
Hiro, not counting "Black Haru", is probably the most confrontational and aggressive of all the cursed Sohmas on the outside. He is also somewhat like Kyo Sohma. Though seemingly very brash and stubborn for his age, on the inside, Hiro is still just a young boy learning how to cope with complicated issues along with bearing the weight of the Sohma family curse.
Role in the story
Relationship with Kisa
Hiro and Kisa have been together for most of their lives. Partially because of this, Hiro developed a very deep crush on Kisa. This was not a problem until, not knowing the consequences, Hiro told Akito Sohma that he really loved Kisa. Akito then physically beat Kisa one day, inflicting damage so severe it took nearly 2 full weeks for her to heal completely. After that moment, Hiro, blaming himself, tried as hard as possible to distance himself from Kisa. He still blames himself for the incident. Unfortunately, just as Hiro was distancing himself, Kisa's classmates turned on her, beginning to tease her mercilessly. Not being able to come to Kisa's defense added insult to injury for Hiro. He wanted to help her, but he feared being the cause of any more of Kisa's pain.
Relationship with Tohru
Unluckily for Tohru Honda, she did for Kisa what Hiro wanted to do— help Kisa recover. Kisa became so enthralled with her that Hiro became jealous. Without knowing any other option, Hiro decided that he would be the terror in Tohru's life. After greeting her on her way to work, he made off with a notebook containing her mother's picture. With Kisa's help, Tohru was able to get the notebook back. The incident also revealed to everyone Hiro's true feelings. As Momiji Sohma explains, "Hiro was jealous of Tohru, and for a 6th grader that sort of thing can be hard to handle. He needed to vent." As "punishment" for taking the notebook, Tohru hugs Hiro and we find out finally which zodiac animal Hiro is: the sheep.
Despite Hiro's aversion to Tohru, she was also able to help him. Hiro, even after telling Kisa his feelings, still felt guilty about Kisa getting hurt because of him. Then Hiro finally confronts Tohru. He tells her that she's ordinary and then asks her if the rumors are true. Can she really solve anyone's problem and heal his or her pain? Hiro unknowingly voices some of his thoughts near Tohru. He thinks he is a coward because he couldn't help Kisa. He hates that he is a powerless child, and he wants to be grown-up. Tohru tells him that he is actually amazing for even being able to admit that he is still a child; it takes a significant amount of courage. Tohru tells him that with his bravery, he will someday be a prince that can always protect Kisa.
In the Manga
Several events profoundly affecting Hiro's character occur only in the manga.
In volume 10, Hiro gets a call from his mother, who tells him she's pregnant. Because his mother, Satsuki, tends to be absentminded and rather ditzy, he demands to know if it happens to be one of her famous misunderstandings. However, what she is saying is true and when all Tohru, Kisa, and the other Jyunishi present find out, they decide to congratulate him because he will be a older brother soon. As they celebrate, it is also revealed that Hiro's sister or brother will not be cursed because all thirteen possible Jyuunishi are still alive and another member will not be born until another member of the zodiac dies. Hiro's sibling turns out to be a girl, whom they name Hinata. His mother jokingly remarks to Kagura's mother that Hiro is so helpful with Hinata that she fears Hiro will develop a "sister complex" with her.
When Isuzu Sohma is pushed out the window by Akito, Hiro is the only witness and the only one other than Akito and Isuzu who know the truth behind the incident. Isuzu forces him to keep it a secret from everyone else because she does not want Hatsuharu Sohma, whom she loves, to remain close to her and get hurt as well. When Isuzu disappears for several months, Hiro confesses before Hatsuharu and Kisa the truth in hopes that Hatsuharu can save Isuzu from her own self-destruction. The confession leads to an admission to Kisa that he angered Akito by telling Akito he cared about Kisa, which resulted in Kisa's own injuries. Both these incidents illustrate the amount of growth seen in Hiro's character, since he now has the courage to admit his feelings outloud rather than venting them through other means.
In chapter 118, he is also seen being freed from the curse, proven as he hugs his baby sister for the first time and receives a hug from his tearful mother without transforming. Reasons as to how or why this happened are as of yet unknown.