(Emotionally steady iceberg master x intermittently irritable demon girl disciple)
(1v1, tragic romance, a master who rewards and punishes fairly, a troublemaking female disciple, two souls in one body, twin-soul setup, male master and female disciple, the heroine runs two schemes at once and is devious beyond measure. A poison pit involving a black flood dragon's demon core leaves the master in an indescribable state. His blood pressure soars, and he resents having such a fragile disciple.)
Xi Ye discovered a pattern: by day, the merciless Sword Sovereign was an iceberg; at night, he would tend her wounds, take her down the mountain to see the lanterns, and forbid her from calling him Shuying. She had to use his courtesy name, Zhaoxue.
Xi Ye: I've lost half my memories. I did it on purpose~
The Sword Sovereign thought he had a heart demon, only to discover he was jealous of himself. After the world went through a rewind, he refused to let this rebellious disciple die, either.
