Aiko is the reluctant love interest of Goro Mori since her hiring as a girlfriend in Stone Skipping. She lives with her father, Masurao, who secretly runs Immigration Bureau plans out of their home. Part of this includes Aiko, whose genetic components are a Bureau project in itself.
When playing the part Mori's girlfriend, Aiko pretends to be a shy, easily embarrassed, and emotionally dependent young girl to suit Mori's prior lies. Afterwards, she becomes all business and cold to Mori as he pays her. She also gives a 'gift' to her clients so her friends and classmates won't suspect she has stooped so low as to sell herself as a girlfriend. The items sold come from her home and she is fluent in lying to her father about not knowing where the various things disappear to. In the final episode, Aiko's personality takes a turn for the better. The destruction of the city and her realization that she can stop it sends her running into action. When Mori starts running beside her and offers to help, she accepts without any of the previous rudeness she displayed. Once the time to save the city comes, she starts the process at the cost of her body without hesitation. Her body seemingly becomes roots that stop the Medical Mechanica factory, but a pumpkin sprouts out and opens to reveal she is alive. She lands in Mori's arms, agreeing to become his girlfriend for real and calling him a dummy as they laugh gleefully together, a significant change from her old attitude.
Aiko is a short, slender girl with big, turquoise eyes and long, powder-blue hair. She wears her hair, which reaches down to her hips and curls up at the ends, up in what appears to be a bow with two leaves connected by a gold spot. She also has messy bangs separated into three parts along with two stray hairs that stick out from behind the tops of her ears. She sports a small, red belt to secure her airy clothes, which are a long, plain-white skirt and matching tank top-esque top. Seemingly a fan of jewelry, she wears green, jeweled earrings with gold studs and a thin necklace with a red jewel inlaid in a gold border.
When being used as a transmitter, her eyes display green static, her mouth hangs open and her "bow" sprouts upwards into a giant, plant-based transmission tower.
Aiko first appears in episode 3, posing as Goro Mori's girlfriend for a day. In an attempt to impress his friends, Mori hires her to play a shy, often-embarrassed girlfriend during their beach outing. She remains introverted while others play and holds onto an "emotional support plant" that's almost larger than her. Given her appearance and good acting, the others believe her to be sincere, but question how a girl as cute as her wound up dating a guy like Mori. It is this suspicion that leads Marco to follow them to the train where Mori was supposedly seeing her off at the end of the day. There, he witnesses a personality change in Aiko as she demands her money for the long day's work, giving him the plant in exchange so none of her friends will catch on. A short scene plays at her home where her father, Masurao, questions where their house plant went, only to be brushed off by Aiko and returns to a room to be scolded by Eye Patch in a video call about its importance. She is also seen briefly in LooPQR at the fair exchanging her services for a bear carving.
In the final episode, Aiko packed all of her things in a hefty bag, leaving Mabase's chaotic destruction at her leisure when she spots Masurao and Eye Patch. They've been pinned under a building and are about to be mummified by the raining mochi. Her father gives her a jack-o-lantern, insisting she take it and telling her she is "free" now. Once they are overtaken by the goop, Aiko decides to find the plant she sold, seemingly recognizing its importance now. Mori finds her, telling her he gave it to Ko Ide and agreeing to guide her if she'll be his real girlfriend. The two, as well as Hinae Hibajiri, reach Ide's home and quickly find the plant. It reacts to her as she holds it, sending the leaves on her head sprouting up into a radio tower with Canti being the receiver. Hinae's words are heard by Hidomi through this connection, starting a conversation between the two. Once back in control of her body, Aiko has Mori take her to the Medical Mechanica iron. With no explanation, she presses her back against it and drops the plant so its pot breaks, causing another reaction that turns her body into roots. She is seen smiling at Mori and Hinae as she roots the iron to the ground, saving Mabase's remnants. It is assumed this process killed her, but she escapes the roots' hold without any indication of negative repercussions to the process, much to Mori's delight.
The plant Aiko 'sold' to Goro for her services appears to be of the utmost importance to a plan her father is a part of. However, it isn't until episode 4 that it is revealed to be an N.O. device made from Canti’s robot shell. When hit on the head with it, Ide's N.O. channel opened "in reverse", which began sucking in Haruko and Jinyu. It is connected to Aiko somehow and can serve as the catalyst for her transmitter activating, creating a communication channel that can cross through N.O. dimensions. This function requires Aiko's body, which can receive sound, and Canti's screen, which receives picture and sound. It also alters her body when the pot is broken by her, causing her body to turn into roots that are likely meant to stop Medical Mechanica's factories. She does so in the last episode, glowing green from beneath the roots as her body continually transforms and grows, but survives and returns to normal when a flower blooms to drop her (unharmed) into Goro's arms.
When first hired by Goro and introduced to viewers, Aiko comes across as incredibly shy, sensitive, and easily embarrassed. Goro also gets this concept across to his friends when she's not around, telling stories about how adorably clingy and dainty she is. However, it's clear to even his friends that this is a little too perfect for him, and Marco sees this when he follows them to a bus stop. Aiko's demeanor changes to a strict businesswoman to get her payment, which depresses Goro when the fantasy ends and he realizes Marco had seen it. Goro has a very low point that day as a result, but when he next sees Aiko as the city is under attack, he's all smiles. He helps her find the potted plant she needs, as well as biking her and Hinae up a mountain - an event so intense that the bike itself falls apart before they arrive at the iron. When Aiko starts towards the iron, Goro has a quick exchange with Hinae in which he says he prefers to call Aiko "unique" rather than the somewhat slighting language she used. As Aiko's body turns to plant-like roots, Goro begins to cry, mourning the loss, but scrambles to catch her when he realizes she's being dropped by the roots. Naked and alive in Goro's arms, Aiko begins to giggle uncontrollably, agrees to his request to be his "real girlfriend", and calls him a dummy.
- The practice of being a rented girlfriend is can be referred to as "escorting" in the west and "enjo kosai" in Japan. (verification needed)