Digimon Adventure V-Tamer 01

Digimon Adventure V-Tamer 01 (デジモンアドベンチャーVテイマー01) was the first and longest-running Digimon, printed in the pages of magazine. Starting on November 21, 1998, it ran to fifty-eight chapters and ended on August 21, 2003. This manga introduces the character of Tai Kamiya, an alternate Tai to the one that features in the Digimon Adventure TV series.

Plot
In this universe, Tai is involved in a V-Pet tournament, where he is told he cannot play because the Digimon in his V-Pet isn't recognized as being a real Digimon. However, after the tournament is over, Tai plays the winner of the tournament, a boy named Neo Saiba, and their battle ends in a tie—something that is supposed to be impossible. Soon after, Tai is summoned to the Digital World by Lord. There, he meets the mysterious Digimon in his V-Pet, Zeromaru the Veedramon, as well as one of MagnaAngemon's servants, Gabo the Gabumon. Gabo brings Tai and Zero to MagnaAngemon's castle, where the pair learn that they are needed to find the five V-Tamer Tags and defeat the evil, who has disrupted the peace of the Digital World.

As they collect the Tags, Daemon brings his own group of humans to the Digital World: Neo, his sister, Rei Saiba, and his lieutenants the Alias III. Neo is chosen to raise Daemon's Ultra DigiEgg, while his sister Rei possesses a that will allow the Digimon in the egg to digivolve past Mega. Rei teams up with Tai while the Alias III and Neo try to defeat him.