Ryuuhou is a well-known and respected tattoo artist. It's implied he's been working as one for many years. His work is the admiration of many aspiring tattooists, often being highly detailed and containing smooth, intricate patterns.
He and Koujaku have know each other from way back when Koujaku left the island with his mother. Much to Koujaku's protests, his father asked Ryuuhou to tattoo his son. At the time, Koujaku was only around fourteen to fifteen years of age. Wanting to test out a new method of human control given to him by Toue (that was not yet perfected), Ryuuhou happily accepted, using Koujaku as an experiment. He ended up drawing large, pink lotus flowers on a majority of Koujaku's back and a black pattern on the right half of his body. The events that occur afterward lead Koujaku vowing vengeance, wanting Ryuuhou dead. Years later, Ryuuhou moves to Platinum Jail, residing in Flame Willow. Finally he is killed by Koujaku.