Digimon Adventure 02
Betamon is the Digimon partner of Michael, one of the DigiDestined children from America, who became a DigiDestined when he saw a Gorillamon. He and Michael are first introduced to the DigiDestined by Mimi Tachikawa and Palmon, as Michael and Mimi are dating at the time. Betamon digivolves to Seadramon when Digitamamon's diner is attacked by a Gorillamon under the influence of a Dark Spiral, with Togemon helping to remove the Spiral.
Betamon shows up again later when Digimon begin to appear in the Real World around Christmas time. As Seadramon, he battles a Cherrymon at Rockefeller Centre with help from ExVeemon, Lillymon and the other American DigiDestined's Digimon. Betamon is involved in the final battle against MaloMyotismon.