Datsumon looks like a biyomon the only difference is that it's blue and tips of its feathers are red, Biyomon the opposite. Datsumon is always a male. Datsu means in hiragana text: fight. Datsumon is specialist in thunder and wind based moves and attacks.
Datsumon appears as a Mataumon, late he digivolved to Datsumon, when he and Kasper where attacked by a Ogremon. Rasmus and Metamon came to their aid, and defeated Ogremon, Datsumon is seen several times in the real world with Kasper.