The so-called Curse-Killing Technique was a branch of the Talisman Arts, and in essence, it differed little from ordinary spells. In fact, it was far more powerful, often killing in a single strike and surpassing ordinary Talisman Arts by a wide margin. But such overwhelming power demanded a corresponding price: every casting carried the risk of backlash. Ordinary spells might not be as powerful, but at least they were safe.
Moreover, miko who practiced the Curse-Killing Technique were often more susceptible to demons' temptations than ordinary miko. It was a hunger for power that drove them to practice it in the first place, so it was hardly surprising that miko with such a mindset could be led astray by demons. For that very reason, they were more likely to fall into darkness and become Black Miko.
Yes, a miko who practiced the Curse-Killing Technique was not necessarily a Black Miko, but she was certainly more likely to become one.
In Han's memories, Tsubaki had always been proud and powerful. Of all the miko training at Kiyomori Temple, Tsubaki alone had been favored by their Master. Their Master discouraged the practice of the Curse-Killing Technique, yet tolerated it because the one practicing it was Tsubaki. Back at Kiyomori Temple, Han had once joked with Gardenia and the other miko that if she had been the one practicing it, their Master would probably have driven her out long ago. Besides, among all the young miko at the time, Tsubaki alone stayed at their Master's side almost constantly. The others mostly trained on their own and exchanged what they learned among themselves. Because of that, none of them had really known Tsubaki well.
But Han could never forget what Tsubaki had said to her when they left to continue their training elsewhere. "Anyone