Doukoku is the big bad in Shinkenger, and he's just a badass. Sealed temporarily by the Shiba Clan's 17th lord, he came back approximately 17 years later to reek havoc on humanity. He has more of a tough guy, fearsome, intolerant attitude in comparison to many recent Sentai villains. He's also one of Sentai's biggest drunks and is seen regularly drinking Sake. Despite being short tempered and usually in a state of rage, he has a soft spot for Dayuu and the music she plays on her shamisen. Ultimately, when he fights the Shinkengers the first time, he just beats the crap out of them. The only thing that stopped him was that he quickly ran out of water.
Dayu is perhaps the most well developed villain in Shinkenger. She is half human, half gedoushu. Originally, she was full human and obsessively in love with Shinza, a man that never loved her back. Eventually finding out that Shinza loved another woman, she killed Shinza and his love interest. This led to her soul falling to Gedoushu. Shinza's soul was trapped in her Shamisen, and often Dayu would play sad music on it. She later developed feelings for Juzo, but couldn't give up Shinza because it would end her existence. She developed a rivalry with Mako/Shinken Pink, who sympathized for her after seeing a vision of Dayu's past in the dream world. Ultimately, she was sacrificed to give Doukoku human life, which made the sealing character useless against him.
Juzo is a menacing, cold-blooded figure. Like Dayu, he's half human and was formerly full human. But unlike Dayu, Juzo can still switch from human to Gedoushu form. In his human life he was a master swordsman who ultimately ended up killing his opponents for pleasure. When he became sick, he entered the Shanzu River which cured him which also turned him into half Gedoushu. He then discarded the last bit of goodness he had in him. He's a stray gedoushu, a bit of a lone wolf. He yerns to fight a swordsman of equal skill level to fight. These fights are pleasurable for him. He would find his opponent in Takeru/Shinken Red, which initially angered Doukoku because Takeru was at the time thought to be the head of the Shiba clan. Juzo had two major sword battles with Takeru, one in episode 26 and one starting at the end of episode 45 and lasting through episode 47. These two sword fights are awesome, among some of the best swords fights in Sentai. His katana, Urasama, is made with the souls of his deceased family members.