This is a world of puppets and puppet masters. Of course, there are also ordinary humans. When Sawada Tsunayoshi was four years old, he concluded a soul contract with someone else and became that person's soul puppet.
Tsunayoshi, who had just entered high school, encountered many unsatisfactory things. His parents also died in a car accident, leaving him with only one brother, Reborn, who had no blood relationship with him. However, Reborn never came to him in the past three years. Everything was conveyed by Reborn's doll Bajir.
Finally, in the academy in Italy, the person who made a soul contract with Tsuna appeared.