Please note that this is basically a very short summary of what happens in Genrou Den, the novel about Tasuki's life before Suzaku no Miko arrived. I also included part of the manga in here as well, right up until Tasuki reveals himself to be the fifth shichiseishi. I have heard a rumor that this novel, as well as the other novels that came after it, will be animated, but this is not solid information.
Kou Shun'u was born on a small farm at the base of Mount Leikaku to his mother, father, and five older sisters. Apparently, Shun'u has gotten to dislike the taste of milk because he was smothered by his mothers enormous breasts, and a dislike for women in general from growing up with six of them. Chances are, he was treated horribly by all of his sisters, as indicated from Kou Adiou... who often beats Shun'u up with logs in retaliation of her little brother calling her an 'old maid.'
Eventually, this horrible lifestyle lead Shun'u to leave home. He was wandering the forests of Mount Leikaku when some bandits stole all of his possessions, including the shirt off of his back. Left vulnerable, Shun'u was saved by an impressive man with a fan; Hakurou. Shun'u was incredibly in awe and so impressed by Hakurou, that he begged to join Hakurou's group of bandits. Hakurou refused, but when Shun'u arrived at the stronghold before Hakurou himself, the bandit reconsidered, and let Shun'u join the Mount Leikaku bandits, and gave him the name 'Genrou.'
Shun'u, now going by the name of Genrou, worked hard at every task given to him. He was to share a room with Hakurou's right hand man, Kouji. Kouji at first, disliked Genrou... so he piled all of the hard labour on the kid. He was jealous that Hakurou had seemed to favour Genrou, but the two became close friends after a while. Genrou practised all sorts of unique fighting skills; archery, judo, swordsmanship, and even plain old brawling. Eventually he moved up higher and higher in rank. Hakurou also revealed to Genrou that he was the Suzaku no Shichiseishi Tasuki, because the mark on his arm signified it.. He also told Genrou that one day, the Suzaku no Miko would come and he would have to leave. Genrou said that he would never do that, and would always stay with the Mount Leikaku bandits.
The day came when Hakurou had to choose a successor. He told Genrou and Kouji that he was falling ill, and told them to fetch a treasure from a rival group of bandits; the Mount Kaou bandits. Whoever brought back the treasure first would be the one he would choose as successor. It just so happens that Genrou and Kouji ended up working together to bring back the treasure (which happened to be the leader of the Mount Kaou bandits' sister, Reirei). A few more incidents with the Mount Kaou bandits occured, including them taking the sacred tessen from the Leikaku bandits.
In the end Hakurou decided to let both Genrou and Kouji be the leaders just as long as they brought back the tessen from the other bandits. Reirei, who had been staying with the Leikaku bandits, and Genrou and Kouji, on her own free will was killed by a demon who had been trying to get the tessen for Ougi, Hotohori's brother. Genrou became enraged and fought the demon while Kouji tried to use the tessen. Kouji failed because he didn't know all of the magical words needed to use the tessen. However, Genrou could use it because he had stronger chi from being a Suzaku no Shichiseishi. Once the battle was over, Genrou left to find a cure for Hakurou's illness.
While Genrou was gone, Eikan, one of the bandits, decided to take over after Hakurou died. He was able to use the tessen because he over-heard Hakurou telling both Genrou and Kouji before Genrou had left. Everyone was afraid of opposing Eikan because of the tessen. Eventually, a girl showed up claiming to be the Suzaku no Miko. She was there with two others; Hotohori and Nuriko. Deciding that one of the shichiseishi had to have been in the group of bandits, the girl, Yuuki Miaka, began to act firey... so much so that Kouji had taken her to Eikan since the big slob wanted one of the girls.
While Eikan attempted to take advantage of Miaka, Hotohori and Nuriko broke in to save her... but suddenly, Miaka dissappeared! Actually, it was Genrou who had whisked by with his amazing speed, and had taken Miaka away from Eikan. He said that if Eikan wanted his 'bride' back, that the two would have to fight. He then left. Returning to his secret base, Genrou and Miaka hid. Miaka tried to see if there was a character on Genrou's body, but she couldn't find one. When Kouji arrived, they told Miaka of the troubles involving Eikan, and the Suzaku no Miko decided to help out, being the chipper girl she is. They managed to get the tessen back from Eikan, but Miaka was still to no avail in her search for the Shichiseishi. Genrou told her that it was Hakurou who was in fact Tasuki, the fifth Suzaku no Shichiseishi that Miaka was looking for... but he was dead.
Miaka decided to head to a village up the mountain that had rumors of a woman who could bring the dead back to life. Unfortunately, they found out that she couldn't leave the village, so Miaka, Hotohori, and Nuriko began to head back to the bandit's stronghold... only to seemingly get lost and be attacked by zombies. Fortunately, Genrou showed up and toasted them all, revealing to them that he was in fact Tasuki. He explained that he couldn't just leave the bandits on their own, but talked it over with Kouji and left him in charge. Miaka then fell sick and all three Shichiseishi headed back to the village.