Five and Nine are among the main characters in the anime ‘Terror in Resonance’ or aka ‘Zankyou No Terror’. Nine is one of the 2 protagonists(other one being Twelve) of the anime. Nine and Twelve form a mysterious terrorist group called ‘Sphinx’ and carry out terrorist attacks in Japan to draw attention to their cause.
Now, Five along with Twelve and Nine were among the 26 little kids who were used as test subjects for the Athena Plan. These little kids were kept in an institution called the settlement and were drug tested. The drug Caveat had a disastrous impact on the health of those kids and all of them died apart from Nine, Twelve and Five. Nine and Twelve cause a fire to create a distraction and take down the security system in order to escape the settlement. They manage to escape the settlement and Five is following them initially but she is left behind. Five could have gone along with the Nine and Twelve but for some reason she chooses to stay in the institution.
Now, the most probable reason as to why Five chose to stay behind was probably so that she could beat Nine later in future. Five for some reason felt competitive with Nine and her reason to live was to win against Nine. At that point of time, Five chose to not remain friends with Nine and Twelve. Most likely, Nine must have always outperformed Five in tasks or games because of which her aim in life was invariably to beat Nine someday. Maybe she was seeing far into the future where in she thought of scenarios where she would get to compete with Nine in a real life situation which is what happens in the anime. Five is able to survive all of the tests performed on to her in the settlement until the Athena Plan is shut down after US govt. intervenes and she is taken into custody by an American agency.
Five is a government operative and a nuclear scientist under Nuclear Emergency Support Team who comes along to assist with the terror attacks although her intentions are to actually compete with Nine. Nine often gets flashbacks about Five. Somehow, he is subconsciously aware of the fact that Five poses a threat to him and Twelve even before Five officially enters the scene. Rightfully so, Five does interfere and create problems for them later on.
At first, it seems like Five had a romantic interest in Nine because Nine seemed the reason for her to be alive. However, her aim was only to win against Nine in games she created herself. Five’s health deteriorates as time passes by because of the side effects of the drug that she took in the settlement. Her desire to beat Nine is probably what pushes her to move forward. She faints after the police shoots bullets at Nine because she wants Nine alive. The reason behind this could possibly be that she wanted to beat Nine by herself and have the true satisfaction of doing so which she couldn’t have got had Nine been killed by the Japanese police instead of her. It could also be that she wanted to meet Nine one more time. It is quite possible for her to have romantic feelings for Nine as she doesn’t kill him in the end because she wants him to remain alive. Although, her ambition to defeat Nine trumps her romantic feelings if there are any.
After chasing down Nine in the car, when she gets in a position to shoot him she chooses not to do so. In her opinion she feels that she has won the game. She then proceeds to kill herself as she feels she has accomplished her purpose. So that is the story of Five and her relationship with Nine.