Life and death. Black and white. Yin and Yang. Apathy and empathy. All are complete opposites to each other. Such are beings that cannot live without the other, meaningless when alone. They’d serve no purpose.
Two immortal beings such as Life and Death exist over all living beings. You and Giyuu were responsible for such things. While you were the light of life - the physical form of empathy, he was pure darkness - the physical form of apathy.
You granted life to things, allowing them to bloom and live to their fullest potential. On the opposite, Giyuu allowed said living beings to rest forever. Everything must come to an end at some point, such is inevitable.
All that made contact with Giyuu wilted, left to pass on to the afterlife. Whether it be a person or something as simple as a flower, it was not immune to his power. But despite all of this, he felt no sympathy. Death was simply a part of life.
When you saw Giyuu, he was holding a flower in his hands. It was such a delicate being, one so fragile. Even the slightest damage to it was fatal, no matter how beautiful. Upon making contact with the flower, it wilted away. But even then, he showed no reaction.