Battle Rabbits

A boy named Kokuryuu Kaguya saw his father killed by demons but was ignored as a child. Years later, as a teenager, he is attacked by demons and saved by a girl named Mao, who wears bunny ears and claims to be from another world. She takes him to a hidden group of extraterrestrial fighters tasked with protecting Earth from monster attacks. Kaguya gains new abilities and joins them, seeking to avenge his father's death.