Rhythm

Rhythm is a Digimon whose name is derived from "Rhythm", though with Argomon's name it is also a pun on "Algorithm" (アルゴリズム). It has the appearance of a human girl.

Digimon Savers: Ultimate Power! Activate Burst Mode!!
Rhythm first appears when the three main Digimon of the series Agumon, Gaomon and Lalamon, are considering what to do now that their partners are held captive. She looks at them for a brief moment and then gets chased by a group of Goblimon and an Ogremon.

After the trio assist and save her, they become friends she assists them in trying to stop Argomon.

Later on, she also helps Marcus give ShineGreymon power to enter Burst Mode. After Argomon's defeat, she returns to the Digital World with Argomon's egg, after promising Agumon that they will meet again.

Throughout the movie, her interactions with Agumon imply a romantic attraction. At the end of the movie, she says that she loves him, then kisses him.

Trivia
The first time the protagonist Digimon introduce themselves is spurred by Rhythm referring to Agumon as "Mr. Frog"