Lulu Hinagiku

Futakoi:
The youngest twins in the series who live with Nozomu, their mother Miyabi, and pet goat Billy. They are affectionate towards Nozomu and claim him as their future husband which makes Billy jealous. [Wikipedia]

Futakoi Alternative:
Lulu Hinagiku is one of the pair who are the youngest twins in the series. She along with her sister Lala appear to be involved in some sort of Military Special Operations, being experts in various weapons from handguns to rifles, and even explosives and rocket propelled weapons, carrying all their weapons in their backpacks. They appear in the first episode locked in a battle against an invading alien on board a stricken military transport plane, before they detonate the plane and bail out with their parachutes.

(Source: Wikipedia)