It was not like fighting a princess. It was not like fighting a dragon, either. A dragon may be a monster, but it is one that comes with a promise: [i]defeat me, and you shall gain my treasure[/i]. There is a treasure to be had in this victory too, but a much humbler one: The story is over. This terror from the ancient past and distant space is gone, torn apart into shreds of mana. You no longer need to care about what it thinks. You no longer need to entertain its confused cruelty. It breaks hard and its essence flees and the world is safe. Like taking out the trash, it was a chore, and chores are beneath the delicate hands and beautiful hearts of foxgirls - but every so often one has to be done anyway. 

And just because the victory is humble does not mean it is not satisfying. To look at the world and think: clean. Safe. Nothing left to do. Just a huge stretch of luxurious nothingness lying ahead, weeks and months where nobody - not even your own mind - will ask you for anything. 

But, while you're up here, of course the thought occurs: you could keep the tails. Nothing says you have to give them back! Well, obviously it'd be the right thing to do, but... it wouldn't be the [i]wrong [/i]thing to do either. Actia and Cyanis would be mad and they'd swear vengeance and come after you, but they wouldn't be coming after you like you were a monster. They'd be coming after you like you were a dragon. They'd find a princess knight and convince her to fight you, and she'd be hesitant at first but you would use your new powers to take over a castle and kidnap a maiden and then she'd have no choice...

You should seriously consider it. After all, you worked really hard to bring a new power into the world. You should be free to appreciate it for a while, before it passes onto someone else. Because that's the difference, isn't it? In a dance, someone leads and someone retreats and power passes back and forth; the weak become strong and the strong become weak. That's just my suggestion, but I think you would have an amazing reign of terror <3