Jeremie Belpois (also spelled Jeremy Belpois) (pronounced as "Jerr-mee Bell-Pwah") is the deuteragonist of Code Lyoko, and a Lyoko Warrior. Jeremie is 12 years old at the start of the series, but with the intellectual and scientific, gifted and talented mind of someone far beyond his years. He acts as the guide in Lyoko, since he is able to run the computer that no one else can (besides Aelita). It is also Jeremie's discovery of the Supercomputer that commences the group's quest to materialize Aelita into the real world, which is revealed in X.A.N.A. Awakens. He's noble, but sometimes has a short temper. He is also the most vulnerable to being possessed by X.A.N.A., the reason for his susceptibility is unknown, but it is believed that his lack of experience in fighting X.A.N.A's monsters on Lyoko may contribute to this.
Jeremie is first introduced as part of Odd and Ulrich's class. He succeeds in every class, except Gym and Italian, and is considered a gifted student by a lot of teachers and the school psychologist, who decides that he needs to go to a special school for gifted children (as seen in Plagued). He is often considered, and sometimes for good reasons, the teachers’ pet, and therefore he had few friends before befriending the rest of the Lyoko Warriors. Jealously looked upon by Herve, one of Sissi's group members, Jeremie is perceived as a boring and inaccessible intellectual by the other school kids, except his group of friends. Despite this, however, Jeremie's character is portrayed as a kind and compassionate, somewhat naïve individual, and his friends look up to his brains.
Wearing simple clothes and big glasses, his clothes reflect his modest and discreet character. Nevertheless, Jeremie is nothing of a stereotype because, other than his academic performance, he has a really well asserted personality. His character can be compared to Yumi's, due to their stubbornness and devotion to studies.
An introvert, Jeremie spends most of his time in front of his computer screen, under the friendly glance of Einstein, the portrait of whom hangs over his bed. He spends most of the series programming, and the viewer will often see him going without sleep at night, all to achieve the goal of freeing Aelita and destroying X.A.N.A. once and for all. If not working, he is often conversing with Aelita, for whom he develops particular feelings as they spend hours talking, with Jeremie enlightening her about the "real world" to prepare her for her future life on Earth.