After Tohru Honda finds herself moving into the seemingly normal Sohma household, all the Sohma family members around her begin unexpectedly transforming into animals. The family members affected by these transformations discreetly refer to it as the "Sohma Curse."
The Fruits Basket storyline revolves around this curse and the characters afflicted by it. So what exactly is the Sohma curse, and how did it first start?
God and The Zodiacs
The twelve Japanese zodiac animals in order are the Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, and Boar. In Fruits Basket, these zodiacs are reincarnated as humans in the Sohma family clan. According to the zodiac legend, a god-like man with unique powers lived alone atop a mountain, and he was very lonely.
Then, after a cat befriended him, he invited all the animals to a banquet. Only the 12 zodiac animals and the cat attended the banquet, and they promised to all gather together on every full moon. Eventually, the animals grew old and close to death, so the man created a spell-like potion for all the animals to drink, so they may be reincarnated and stay friends for eternity.
This eternal spell would continue for hundreds of years, causing certain members of the Sohma family to be possessed by one of the spirit animals of the Japanese Zodiac. The zodiac spirits are reincarnated into different members of the Sohma family clan when the previous one dies. This spell is what the afflicted Sohma family members refer to as the "Sohma Curse."
The curse itself is actually a "bond" between the zodiac animals and their "God;" the man they befriended many moons ago. The curse binds the zodiac members to their God, who is also reincarnated into the Sohma family. This invisible bond gives those possessed by it somewhat of a sixth sense; the zodiacs have a deep emotional and spiritual connection to their God that only they can sense and understand.
The Curse
Being possessed with the zodiac spirit has a lot of drawbacks for the host, including transforming into their zodiac animal when touched by the opposite sex or when they are under a great deal of stress/ exhaustion. This makes it extremely difficult for the cursed members to have heterosexual friendships and relationships with people outside the Sohma family.
The zodiac members have to keep their curse a secret from others, which causes them to be distant from others and puts strain on their relationships. This leads to many possessed members feeling lonely, isolated, and misunderstood. Being cursed with a zodiac spirit can also cause tension and issues within the family itself, as parents have to navigate the unique struggles of having a possessed child and sometimes even completely reject the child. However, the worst drawback for the possessed Sohma members is the loss of their freedom and normalcy. Over time, what was once a bond between friends slowly transformed into a tyrannical curse that caused more harm than it reaped benefits.
Even though the most recent zodiac members don't have any memories of the original promise between God and the animals, they are still bound against their will by that eternal pact their zodiac spirits made with God hundreds of years ago. Despite having a strong instinctual connection to their current God, Akito, the zodiacs do not have a positive or healthy relationship with Akito.
Rather than friendships, the relationships between Akito and the zodiacs are ruled by fear. Not wanting to be abandoned by the zodiacs, Akito abused their power of authority as God to manipulate the zodiacs. The zodiacs are controlled by Akito and have to obey Akito's every demand. Akito often verbally and physically abuses the zodiac members, using fear-based tactics to keep the zodiacs in line. The zodiac members cannot defy Akito due to the intense feelings of respect and fear they have for their God. Due to this curse-like "bond" and Akito's selfish demands, the zodiac members cannot live freely. They are forbidden from having romantic relationships, and they must drop everything they're doing and go to Akito when God commands it.
Slowly Fading
Although the original God had good intentions and just wanted their friendships to last forever, he unintentionally created an oppressive curse that caused years of generational abuse and psychological scarring.
His spell had the opposite effect of what he wanted; rather than growing more fond of each other, the zodiacs grew to fear and resent the God. Just as the original friendships and memories between the zodiacs and God are fading away over time, so too is the "bond" holding them all together. With the curse slowly weakening, the zodiacs and their God are unsure of what their futures will hold.