Itadori Yuji is the main character in the manga and anime series Jujutsu Kaisen. He is a student at Tokyo Metropolitan Curse Technical College and a member of the Jujutsu Sorcerer’s team. In the series, Itadori’s age is revealed to be 15 years old.

Itadori was born on November 20th, 2004, which makes him 15 years old at the start of the series, which takes place in 2019. He is shown to be a third-year high school student, which is typically the final year of high school in Japan. Itadori is described as being athletic and physically strong, which is shown through his love for playing sports and his ability to overpower curses with his bare hands.
Despite his age, Itadori is shown to be mature beyond his years, particularly in his ability to handle difficult situations and make tough decisions. He has a strong sense of justice and a desire to help others, which is what leads him to become a jujutsu sorcerer and fight against curses.
Throughout the series, Itadori undergoes significant character development as he learns to control and harness his powers as a jujutsu sorcerer. He becomes more confident in his abilities and gains a deeper understanding of the world of curses and sorcerers.
It’s important to note that in Japan, the age of consent is 13 years old, but there are laws in place to protect minors from sexual exploitation. The series does not focus on romantic relationships and instead focuses on Itadori’s journey as a jujutsu sorcerer and his battles against curses.
In conclusion, Itadori Yuji is 15 years old at the start of the Jujutsu Kaisen series. He is a third-year high school student who becomes a jujutsu sorcerer and fights against curses to protect others. While he is young, he displays maturity and strength beyond his age and undergoes significant character development throughout the series.