after Rookie lands in the demon word he is breifed by Sgt Fox and SSGT Rico Becket (Shadow Force) and assigned to work with HECU operatives but the Demon Forces are launching a covert op against the Wolf Corp Forces and request a human soldier with Delta Force training and Rookie is the only one with that training
the soldiers of the demons hate the fact of working with a human
he is assigned to work with Viper Squad an elite spec ops squad (Sakuya (demon), Sakura (vampire), Yoka (spider demon), Reina (Snake demon) ) its a unit of all girls and they arent looking forward to working with him.
the squad leader Sakuya is friends with the Vampire queen and when the girls were going to find Rookie, the vamp queens daughter ran ahead and triped and dropped her bunny
a soldier picked it up and handed it to her and petted her head and she smiled and then Viper relized that soldier was Rookie