@Kristia
You see, when John saved Ran the first time, he noted that despite her injuries, her tails were still radiant with an aura. They act as a source of power. It would make sense that they would try and remove the tails from Ran, to remove any chances of their power source escaping. John put two and two together. He may be a soldier, but he's not "soldier stupid".:p Spartans are suppose to actually be smarter than your average human, due to their augmented nervous system.


