Doruru

Doruru is a member of Dark Keroro Platoon's Keronian manifestation empire, alongside Dark Keroro and Shivava. Giroro remembers him as one of his old brigade's fiercest soldiers. In the end, Doruru is defeated with Giroro and Natsumi's combined efforts.
Doruru is a blue full-grown Keronian. He has black bags under his eye sockets and the center of his sky blue hat is pointed downward until flattening at the end. The ears of his hat are pointed out and carries double-barraled guns. He wears cannons on his arms and hat. His symbol is a yellow phi symbol.

(Source: Keroro Wiki)