Jan

is a friend of Leo, a young boy who was turned into an Akuma when he tried to bring his mother back to life. After helping Jan realize Leo's true nature, Allen Walker exorcised Leo at Jan's insistence.

Appearance
Of average height and weight for his age, Jan has short brown hair and brown eyes, and is always seen in an aviators hat with the goggles pushed up. He wears a striped shirt, darkly-colored shorts and roller blades.

Personality
Like most children his age, Jan resists authority and has a mischievous streak, such as when he initially idolized Allen Walker until Allen attempted to dissuade Jan from further investigating Akuma, which Jan responded to by throwing one of his 'onion bombs' in Allen's face. Jan is also fiercely loyal to his best friend, Leo, going so far as to throw himself in front of Allen's Anti-Akuma Weapon, Cross, when Allen first attempted to destroy Leo's Akuma.

In the end, Jan knows the importance of Exorcists and of saving Akuma, and is determined to follow in his father's footsteps to rid the world of the Earl of Millennium.

Background
From an affluent family, Jan's father is a scientist for the New World Alliance, the same organization that founded the Black Order. It was through his father's research notes that Jan learned of the Millennium Earl and the Akuma, making him one of the few humans outside of the Black Order who knows of the ongoing war. It is also because of this knowledge that Jan, with careful deduction, is capable of identifying Akuma, even when they're in a human guise.

Jan recruited the help of his best friend, Leo, to utilize the laboratories Jan's father left in their house to study Akuma. Unfortunately, it was because Jan told Leo about the Earl and the contract he forms with those whose loved ones died that Leo became an Akuma, though Jan does not realize the error of his ways until it is too late.

First Meeting with the Earl of Millennium arc
When Allen passed though a town on his way to the Black Order, he was forced to abandon his ride when he heard someone screaming about Akuma. He arrived on the scene to find several people crowded around a young boy, chastising him for telling lies. The boy, however, insisted that there was an Akuma, exclaiming that he had seen the homeless man who was in the group get killed by a "tough-looking guy wearing a hat", and that he had seen an Akuma skeleton enter the homeless man's body.

The accused homeless man quickly silenced the boy, Jan, and insisted that they had been playing a game, making the other adults of the group disperse. Just as the homeless man looked down at Jan, a pentacle forming on his head, Allen activated his Innocence and slew him, showing that Jan had, indeed, been right.

Jan, excited to meet a real Exorcist, tackled Allen in an embrace and began drilling him with questions, explaining that his father was a scientist in the New World Alliance and that he (Jan) had learned about the Earl through his father's notes. When Jan began to ask Allen questions about Akuma again, Allen attempted to dissuade Jan from wanting to learn more, only for Jan to become annoyed and throw an 'onion bomb' in Allen's face, using the distraction to escape.

Not long after he arrived home, Jan was visited by his friend, Leo, whose mother had recently died. Jan attempted to cheer Leo up by telling him about the Earl, whose face Jan had apparently seen, though Leo doesn't speak while listening, a strange symbol appearing in his eye. Jan drew a crude picture of the Millennium Earl and showed it to Leo, and immediately after Leo told Jan he had somewhere to take him. Just then, Allen arrived.

Jan pushed his way past Allen and skated off with Leo, whom Allen noticed something odd about just as the two boys disappeared.

Leo took Jan to a cemetery, and thinking Leo wanted to pay his respects to his mother, Jan went inside, where he bumped into the Earl. The Earl, incensed with Jan for knowing too much about Akuma, explained to Jan that he had turned Leo into an Akuma as punishment, and though Jan refused to believe it, Allen arrived and confirmed it with his Pentacle Eye.

Allen then attempted to destroy Leo, but Jan jumped in the way and shielded him, insisting that Leo wasn't an Akuma. Immediately after, though, Leo took the form of a Level 1 Akuma and pointed a gun at the back of Jan's head. Allen shielded Jan from Leo's blood bullets, and Jan could only listen as Allen and the Earl exchanged words, in shock.

As Allen began to fight, the Earl summoning more Akuma, Leo fled the cemetery and watched from the outside, realizing that Leo had become an Akuma because he (Jan) did not understand the human heart well enough to realize that some people could not resist the temptation of being able to bring a loved one back from death, even knowing the consequences like Leo did. Know knowing his mistake, Jan cried out for Allen to destroy Leo, watching as Allen rent Leo in half.

After the Earl had fled, Jan ran to an injured and collapsed Allen's side and begged him to rest while he went to find a doctor, Jan shedding tears.

Three days later, Jan was seen soldering a metal cross that he would use as Leo's grave marker until people realized Leo was missing and gave him a proper burial. Jan revealed to Allen, who had been recovering at Jan's house, that he (Jan) would be going to his father's offices at the New World Alliance headquarters to study alongside his father in order to become stronger.

Jan and Allen wish one another luck, and the metal cross is seen on a bookshelf next to a picture of Jan and Leo.

Trivia

 * Jan likes inventing things and hamburger and dislikes green peppers.
 * Jean is very similar to Taiyo Yamamoto the main character of Continue.
 * In the anime, he is the son of the Science Division's European Branch member Jake Russell, but in the manga his father is unnamed and works for the New World Alliance.