Professeur Seko is the Pokémon professor of the Hoenn region, appearing in the anime from the beginning of the Advanced Generation story. He is first mentioned by the Johto trainer Harrison, who describes him as the great Pokémon expert of Hoenn, and he is met in person when Ash arrives in the region. At that point Seko provides crucial help by treating Pikachu, who is suffering from a dangerous overload of electrical energy, and his practical knowledge of Pokémon health proves essential to resolving the problem. He also gives the young trainer May her first Pokémon, a Torchic, which sets her off on her journey. He lives in Littleroot Town, where he works in a laboratory with an assistant, but his preferred workplace is the outdoors. His research focuses on the habitats and living environments of Pokémon, and he loves testing his hypotheses in the field rather than staying at his desk. He is a tall, sturdy man with long brown hair tied back, round glasses, and green eyes, and he is consistently shown as an energetic, good-natured and approachable person, with a tendency to throw himself into hands-on situations and a recurring habit of being chased by wild Pokémon while working outside.

His motivations are rooted in a genuine commitment to understanding Pokémon in their natural surroundings and in supporting new trainers as they begin their adventures. Alongside his research, he is responsible for entrusting young trainers with one of the region's starter Pokémon, and he has close personal ties to the main group. He is a good friend of Norman, the Petalburg City Gym Leader and the father of May and Max, and he was trained by Professor Oak, whom he addresses with great respect. He also gave Harrison his first Pokémon, a Torchic, which explains Harrison's high regard for him. Over the course of the Advanced Generation series, Seko reappears on several occasions, including on Myokara Island, at a gathering that brings together the main group and Professor Oak, and during a holiday in the ATO archipelago. He is generally seen traveling by jeep.

His role in the story is that of a recurring support figure who represents scientific authority in Hoenn and helps guide the characters at key moments. His notable abilities include a strong practical knowledge of Pokémon behavior and habitats, the capacity to diagnose and resolve health problems in Pokémon, as demonstrated by his successful treatment of Pikachu, and the experience needed to prepare starter Pokémon for new trainers. Although his core character remains steady throughout the series, his relationships with the main characters are strengthened through repeated encounters, and he later appears in supportive moments in subsequent series, such as watching major battles unfold alongside other familiar faces, which reflects his continuing place in the wider world of the anime.