The second main protagonist of the series. Jean is a young 14-year-old orphan who fell in love with Nadia ever since he first laid eyes on her; unlike her, however, Jean has a completely different personality and interests. He is very generous, patient, friendly, and devoted to the things he loves, which are his friends and the love for science. He is also a genius inventor, in fact he is capable of creating complex machines at a very young age. Jean's father is a wealthy trader and ship's captain, but was recently lost at sea and is presumed dead. (We later find out that there has been a rash of mysterious disappearances of ships lately and the rumors are that a sea monster has been attacking them) Jean, however, chooses to deny them and is determined to finally find his father along with his big adventure with Nadia to find about the Blue Water. Despite being somewhat awkward when it comes to social graces around the opposite sex (such as giving compliments or lack of awareness in some cases where he's inventing and/or reading when Nadia wants his attention), Jean is genuinely well-behaved and is nice to everyone; even Gargoyle finds something to admire about his courage and cleverness. He's openly honest and brave as well. Jean continually looks on the bright side of things; for example, when his only pair of glasses are broken when Nadia accidentally steps on them, Jean immediately tells her not to worry, that it is God's way of teaching him detachment.
His relationship with Nadia is one of the more central aspects of the show. When they first meet on the Eiffel Tower, Nadia refuses his overtures, but when Jean rescues her, he earns her trust. A close friendship forges between the two of them—Jean is consistently loyal to her and vows to take her to Africa someday. Nadia genuinely appreciates his company and attention... to the point where she feels lonely when he gets involved in a project. Later their relationship begins to turn romantic, but Nadia does not know how to express her feelings to him. Nor is she capable of conveying what she wants from him (a compliment for a dress, for instance). This leads to outbursts of anger often misdirected at Jean (in reality cries of frustration at her inability to declare her desires), yet he continually forgives her. (Subsequent scenes following rages involve Nadia feeling bad for her actions. For instance, in episode 10, after unfairly laying into Jean when they have to switch rooms, she apologizes to him.) When she is not brooding over their relationship, Nadia often goes out of her way to do something nice for him, such as cooking, encouraging him to build a gyrocopter, or comforting him when he grieves about his father (in Episode 16). She is also seen to passionately defend Jean in several instances, such as when she verbally attacks Nemo and his crew for reprimanding Jean for endangering the Nautilus due to an accident with one of his inventions, or even more when she allows herself to be captured by Gargoyle on Marie's Island so that an injured Jean can escape. Likewise, each time Nadia gets into trouble, Jean continually rescues her. Occasionally a disagreement will occur between them about certain issues (notably eating meat or the use of technology vs. nature), but they do not last long. As a result of Jean's love, Nadia is gradually transformed as a person; his optimism overcomes her pessimism, and she becomes more trusting, respectful, and caring of others.
That said, Jean also undergoes some growth as well during the show. For instance, he believes that technology can do no wrong, and is quite disturbed by Nemo's description of the Nautilus being a "killing machine." His faith in technology is crushed when a friend of his sacrifices his life in a contaminated engine room. Furthermore, he learns that his father is gone and there is no point searching for him. At that point, Jean begins to consider quitting inventing... until Nadia suggests him to build a gyrocopter. He determines to do so without the aid of grown-ups, straining his friendship with Hanson in the process. Jean eventually realizes that receiving help from grown-ups is just as valuable, and, working together with Hanson, he completes his flying machine and manages to impress Nadia. Furthermore, he is forced to take responsibility for keeping Nadia and Marie alive when they become stranded on a deserted island, going out of his way to provide food, shelter, and care. Jean does not understand why Nadia is so adamant against eating meat, particularly when she mistreats him and Marie for doing so; as such, he is quite confused by her mood swings. It isn't until Nadia finally confesses the real reason behind her hatred of meat that he gains a new understanding of her different view of the world. Even when Nadia later admits her true identity and acknowledges her faults, Jean still accepts her as a person.
