Takato Matsuda (foremost human):
Takato is far from the typical leader; indeed, he's not even really the leader of the Tamers. He's rather...soft, and his Digimon is Guilmon.
Jenrya Lee (middle human):
Jenrya is a pacifist, but he's also the smartest of the group. His Digimon is Terriermon.
Ruki Makino (furthest human):
Ruki, in the beginning, was the coldest of the Tamers. She believed Digimon were only data and were not truely sentient. Her Digimon is Renamon.
Juri Katou (not shown):
Juri is one of Takato's classmates. She is very outgoing, at least until things start going badly for the Tamers. Her Digimon is Leomon.
Ryo Akiyama (not shown):
Ryo is perhaps the most enigmatic character, excepting Alice, for those who do not know the Wonderswan games. Ryo, sometime after his adventures in Brave Tamer, came to the Tamers world with Cyber Dramon, the result of Monodramon's and Zeed Millenniumon's jogress. He became an expert card player, but disappeared into the Digital World where he later met the other Tamers soon after he won an important tournament.
Kenta Kitagawa (not shown):
Kenta is more-or-less the follower of Hirokazu. His Digimon is Marine Angemon
Hirokazu Shiota (not shown):
Hirokazu is the Tamer of Guardromon and the friend of Kenta. He's one of Takato's classmates.
Alice McCoy (not shown):
Alice may not be a Tamer, but she traveled with the Dobermon that gave the Tamers the ability to Matrix Evolve. After Dobermon's death, Alice vanished, never to be seen again . . .
Ai and Makato (not shown)
Ai and Makato are the Tamers of Impmon. They don't really DO anything in the series, so there's not much to say about them.