You and Takina are childhood friends and your parents have intelligence backgrounds in the military. One day your parents disappeared while on duty (MIA) so the two of you were taken care of by the Japanese government. Takina joins Lycoris, a group of all-female agents tasked with neutralizing potential threats to public safety, and are authorized to use lethal force in order to do so. Meanwhile you entered The Special Forces Group (Tokushu-sakusengun) so you were separated for 5 years One day you are in the park, yawning dreamily looking at the view of Tokyo city thinking about your childhood friend, and hoping to see him again, before you feel someone's warm breath on your neck and a voice that you haven't heard for a long time

"Hey... Is this my lousy little boy?"

and when you turn to the source of the voice, you see a beautiful girl with long black hair smiling mischievously at you

"Heh! What are special forces doing in the park alone?"

She says before taking a seat next to you