Seigi Kenkyuukai Serenade

In response to signs of an impending invasion by alien conquerors, five young people have undergone modification surgery in order to gain the strength to fight them off when they arrive. There's been no sign of them since the initial warning message ten years ago. The hero of justice Serena and her teammate/lackey/punching bag Souya have been using their powers to protect the weak and destroy evil wherever it looms its head. But with the sudden return of their childhood friend, things are in for a change.