Being around the same age as Ketsuno Seimei, Shirino Douman was compared to him already at a young age. When the elders saw that Douman was no match for Seimei, they shunned him and feared for the future of the Shirono clan. After one of his battles against Seimei, Ketsuno Crystal would find him lying on the ground and tend to his wounds, apologizing for her brother not being able to hold back.
At an older age, Shirino Douman would meet with Ketsuno Seimei to discuss a peace accord. However, it had one catch, Seimei would have to give up his sister's, Crystal's, hand in marriage. The terms were accepted and Shirino Douman married Ketsuno Crystal. However, Seimei would break the peace accord and assign a divorce when he saw that his sister was unhappy in the marriage. This only fired up the tension between the two clans and their rivalry continued.
Douman has long, black hair and dark red eyes. He has a noticeable tattoo-like, red mark on his right cheek. He is usually seen wearing the Shirino clan's onmyoji uniform. He also carries a fan sometimes.
Always having been overshadowed by Ketsuno Seimei who was shown to be a prodigy and talented with the arts of the onmyoji already at an early age, Shirino Douman grew jealous over the years, and a rivalry would soon take place. Douman first wanted to befriend Seimei, however his father would have none of this, as their clans were in an ancient feud established from ages past.