They seem to have the same father and mother but are not related by blood. Love each other but cannot stay together. Since I can't love, I can't watch him love others and stay a widowed life as a monk.
Although they were born on the same day, she was raised as a boy and became a powerful prince. He was sent to a temple from a young age to become a monk who could never interfere with worldly affairs. When they were fourteen years old, the two of them had a sudden glance that sealed their fate. They were brother and sister and could not fall in love, but they were not related by blood and could only kill each other for their own interests.
She had failed all the men in the world for him, but he had failed her alone.