They both look practically identical as they both have blue hair, but they have different hairstyles. Naoko has short hair, while Houko has long hair. They each have a bow on their head, but it is on opposite sides and with inverted colors. They also wear the normal Hyakkaou uniform with shorts under it.
Both of them act very cheery but are actually cunning and mean underneath that facade. Both of them are also usually quite rude and demeaning when they're about to win. They care little about other people, only about each other.
Naoko and Houko are good gamblers and confident in their ability to beat their opponents. They can take high risks, since they can always work and cheat together. They show to be quite ambitious, as they want to get rid of Aoi Mibuomi and become leaders of Full-Bloom. They are also members of the softball club.
After Mary Saotome is defeated by Sachiko Juraku at Doubt Poker, she finds herself with not enough money to pay the usual fee to the Student Council and is fated to become a housepet soon. After giving the small sum she had left to Tsuzura Hanatemari and Yukimi Togakushi, she decides to give up and accept Sachiko's proposal. As she's about to meet her, Mary runs into Mikura Sado, who suggests visiting one of the various gambling dens that accept players with no money. Thus, the two girls meet up with Naoko and Houko. The twins accept to bet five million yen, the exact sum Mary needs, and declare that in case of defeat Mary and Mikura will have to become their friends. When Mikura comments that they aren't respectable people, they reveal that their true intention is to dethrone Aoi Mibuomi and take his place.
Suddenly, Ouri Shimotsukiuri enters the room and she has been spying on them for a while, even using other students for this purpose, and is disgusted with their insubordination towards Aoi. She threatens to tell him what they have just said about him, forcing them to accept a new challenge. Mary and Mikura reluctantly join in, although Ouri ruined their plan. Because of her, it's now decided that the losers in the fourth and fifth place will become housepets of the winner and the game starts.
At first, everything goes smoothly and they are about to win thanks to their signs; however, Ouri reveals that she knows about their secret way to communicate. At first she says that she noticed it herself after some turns by observing them, but later she admits that she investigated so much that she's now aware of every possible sign they could use. They get nervous, since if that would be revealed their lives as gamblers would be over and they would have to become Ouri's pets. But Mary turns it around and manages to beat Ouri, making Mikura the winner. After their defeat, the twins are devastated but humbly accept their fate, saying they will obey to whatever order she gives them.
However, Mikura has no interest in becoming their owner and tells them to just give Mary and her the money they wanted. They're shocked that their opponent refused to mistreat them.
They are later seen at the Full-Bloommeeting, where they are noticeably less cheerful after their humiliating defeat. Ouri also constantly watches them warily, which makes them nervous. Soutarou Ibuki and Ouri comment that they deserve to be kicked out for thinking of betraying Aoi, which makes them anxious. But Aoi is not angry and tells them he forgives them, especially because he admires how ambitious they are. He says they should even aim to become Presidents of the Student Council. The sisters appear fascinated by his compliments.
During the festival, the twins arrive at Yuriko's club and challenge her to play against them. This is according to Aoi's plan to get rid of the council members, one by one.
- Naoko is the older twin.
- They are apparently extremely busy with softball practices.
- Ougatou means, “elderly woman, mother (嫗) (ou), in the street, leading a group of people (頭) (tou)”.
- Houko means, “near, close, beside, vicinity, proximity, besides, while (傍) (hou), child (子) (ko)”.
- Naoko means, “ordinary, common, straight (直) (nao), child (子) (ko)”.