The player assumes the role of Chris, the protagonist of Popotan. The main characters include three sisters and their maid who live in a western-style mansion. Ai is the eldest of the three and has the ability to communicate with plants. Mai is the middle sister; she is a tomboy and disapproves of Chris's slacker behavior. Mii is the youngest and the most energetic; she often cosplays as "Magical Girl Mii" and helps people out. Their maid Mare appears emotionless at first, but reveals hidden depth later in the story.

Popotan takes place in the distant future within the remnants of Tokyo, destroyed by a cataclysm and since altered by geological transformations. The disaster was caused by a giant dandelion structure resembling a spire that arose in the city atop a hill. The main location of the game is a European-style mansion, seen as completely out-of-place in the city. Much of the daytime is spent outside the mansion wandering around town meeting characters and triggering event sequences.

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Illustration: Poyoyon Rock

Scenario: Seki Shun, Iwashimizu Shin'ichi

Oldest sister and the present landlady of the mansion. She is near-sighted and needs glasses to see clearly; in addition, she has no sense of direction. Ai is a motherly figure who constantly tries to help people. Her easygoing, caring nature often leads her to fail at things because she cannot muster the resolve to criticize others. This is why she allows Chris to stay with them when she finds out he has nowhere else to go. Believing she is ugly and fat, Ai hides herself behind her glasses and by wearing large, loose-fitting clothes. She also seems to be the de facto caretaker of her sisters' pet ferret, Unagi, which often hides under her hat. Ai also loves to take baths, more than once a day if possible. Ai has the ability to speak to plants.

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The sisters' maid. She appears to behave like if she had no emotions at all, especially at the beginning of the game, but Mare later proves that she does have her own desires. She also becomes friendlier with Chris as the story progresses to various degrees, depending upon whether it's her scenario or not. Is disliked by Mai who calls Mare "Roboko" rather than by her name, always threatened to be destroyed or to be disposed of by her

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Her calm, mature demeanor contrasts with her youthful appearance, and thus her age is a mystery. Chris meets her on a stroll at night and brings her back to the mansion. She lacks linguistic skills, and at first not much about her is learned. Because Shizuku is unable to take care of herself, Chris offers to pay her rent as well.

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