Once she got out of the changing room, Touma was surprised to discover that someone else took the place of the usual sport teacher and no-one beside Ty and her seemed to notice. What terrified her was the fact that, while the new teacher looked perfectly human, she could feel it was only a magical disguise similar of her own, that this new teacher was a succubus, like her, and not any succubus either, but one of the 4 queens of hell, or ‘angels of prostitution’ as they preferred to be called.
Between the distance with the other demoness and her human disguise, she couldn't identifies which of the 4 it was, but she didn't think any demon would publicly reveal itself, they accorded too much value to their discretion for this.
Of course she was wrong and, as soon as she passed near her, the new teacher grabbed her and used her magic to forcefully reveal Touma's true nature, not caring that it destroyed her own disguise, revealing herself as Naamah.
While angels are eternal, no demons was, not even the ones daring to call themselves angels. Demons DO grow old, even if they do that far slower than human does. To survives, the the older demons, the ones that used to be angels, regularly stole the body of a younger demon, making it their own. Touma's father, an inccubus, had sold her to Naamah as a potential new body, which prompted her to earth, fleeing that grim destiny, and ultimately meeting Ty and starting to see the errors of her kin.
While Ty flew to his girlfriend's rescue, not caring with hiding his recent ascension to angelhood anymore, the demon queen shouted “WERE YOU REALLY THINKING YOU COULD ESCAPE YOUR DESTINY?!? Most demons would love to have those wings, to be marked as my next body, and like it or not, MY NEXT BODY YOU'LL BE!”
A few second before Ty reached the two demoness, Touma plunged one of her clawed hands inside Naamah and extracted something. For most of the other students, this something was totally invisible, but to Ty, Touma and their few mystically inclined classmates, it looked like a ball of mixed light and darkness.
This ball was the soul of their usual sport teacher, and if front of shocked spectators, Naamah include, Touma seemed to devour the darkness in it. Once it was perfectly purified she handed it to Ty, saying “Give it back to our true teacher!”
Once he had the soul in his hand, Ty flew in the direction it said the body was. Naamah roared something, but neither him or Touma paid any attention to it. What he did pay attention to was how his girlfriend intended to protect their classmates from the demon queen.
Touma knew that, since the first demons were fallen angels, even their descendants sill had most of their angels powers, even if no demons could use those powers without killing themselves. But she also knew it was the only way to end Naamah before she could attack anyone present, the only way to protect her classmates, so she placed her two hands on the evil queen and unleashed all her dormant angelic powers.
Ty had the time to retrieve the body of his sport teacher, Mr. Wilson, give him back his soul, and help him walk back to the rest of the class before Touma ended her assault. The young succubus was surprised that using this powers hadn't even scratched her hands, especially since it had utterly disintegrated Naamah. But even if it hadn't hurt her, it still had greatly drained her. She only got the time to understand that, if she was still alive while other demons died, it probably because she wasn't trying to use said powers for evil, (quite the contrary, even) before loosing conciousness.
Ty grabbed her in one of his wings before she touched the ground. He knew that, in her demonic form, it would take fare more to really hurt her, but that wasn't a reason. Thanks to the one-way link between them, Ty knew her theory, and while he didn't have proof, he did think the same.
Using his magic to amplifies his voice, Ty then asked everyone present to “Please, keep both our secrets between god and us, Touma is sincerely trying to turn over a new leaf.” While doing so, he also silently wished that all of his classmates would accept to do so.