Relations[]
Naota Nandaba[]
To Mamimi, Naota was little more than a plaything for her sexual frustrations and to use as a stand-in for his older brother. Usually, he finds her to be immature and foolish and can be quite harsh to her. Despite this, he develops a crush on her but is confused about how to deal with it. Mamimi did not like it when Naota started stepping out of his brother's shadow and began finding himself; she became cold and indifferent around him as he no longer reminded her of her ex-boyfriend. When he finally realizes that Mamimi will never return his feelings and frankly had enough of all her nonsense, their relationship comes to a messy end. Without Naota in her life she became even more mentally unstable, enabling her to cause even more frequent collateral damage. In an epilogue after the events of the sixth episode, Mamimi showed how sorry she was when she finally called Naota by his real name and was able to end things on good terms when she left Mabase to become a professional photographer.
In the novelization of "Brittle Bullet", it was explained as to why Mamimi did not reciprocate Naota's feelings: despite seeing Haruko and Naota getting closer, it was not jealousy that she was feeling. Rather, seeing Naota hit the satellite out into orbit at the end of "Full Swing" made her believe that Naota was acting more manly. Yet, despite this act improving her perception of him, it also made her no longer want him, as she believed that a man could easily throw her away. In the end, she only wanted a substitute Takkun instead of a manly Naota.
Haruko Haruhara[]
Mamimi and Haruko do not have much in the ways of interaction though in the brief moments they are together they appear to be friendly towards one another, but as Naota's personality changes because of Haruko, Mamimi finds herself liking him less and rejecting him more. While Mamimi never shows any sign of jealousy or anger towards Haruko directly, she does indicate some jealousness towards Haruko for changing Naota in the fifth episode.
Canti[]
Mamimi is convinced that Canti is a god. She calls him "Canti-sama" after "The Lord of Black Flames" in a video game she plays, leading to the rest of the cast calling him by this title throughout the rest of the series.
Shigekuni Nandaba[]
While not much is known about their relationship in the anime it can be implied that Shigekuni did not approve of the relationship between Mamimi and Tasuku and as a result grew to dislike her, with the former not being fond of him either. Despite this, in the novels it is stated by Naota that his grandfather's hatred of Mamimi stemmed from jealousy. Shigekuni is a big fan of baseball and was thrilled to see his eldest grandson not only share the same passion but also be naturally talented in the sport. However, once Mamimi came into the picture he feared that she would take Tasuku away from him and end up letting his talent go to waste.
In the novelization of "Fire Starter", upon seeing Mamimi in the yard with Naota and Haruko, he decides to mock her by bragging about the new clothes that Tasuku had sent him from America, knowing that she had not received any letter or phone calls from him. After she takes a picture of Canti, he yells at her and claims that she has no right to take pictures of the Nandaba's robot, before threating to call the police on her.
Tasuku Nandaba[]
Mamimi first met Tasuku when he saved her during the burning of their school, an event later revealed to be caused by Mamimi herself. The eldest Nandaba brother has clearly had the largest impact on Mamimi from the start of FLCL. She believes herself to be his girlfriend, or at the very least his ex-girlfriend and is clearly obsessed with him. From nicknaming everything "Ta-kun" to her closeness to Naota, Tasuku's leaving is the center of her world. She spends a majority of the series trying to replace him through intimacy with Naota, sacrifices and finding and naming pets. After learning he has an American girlfriend, she went into emotional distress then collapsed which she referred to as "overflow". By the sixth episode, Mamimi realized Tasuku was never going to call or come back for her as she let the terminal core eat her cellphone which had his number on it and later, she departed from Mabase seemingly having moved on from him.
Despite this however, Mamimi had actually kept in contact with Tasuku in the manga and is stated to have remained in contact with him via her phone in an early proposal document in The FLCL Archives.
Takkun[]
Takkun is a stray cat that Mamimi took everywhere with her. Since she isn't allowed to keep pets at home, Mamimi kept him under the Mabase bridge where she hangs out. He shares his name with several other things that Mamimi tried filling the void with as a result Tasuku leaving. At first the cat seemed to be fond of her, but eventually left her when he found a female white cat to be his mate. It's possible that he left her because she didn't feed him as she had asked Naota if he had any cat food on him in the second episode, and knowing she asked for day-old bread from the Nandaba Bakery then it's very likely she couldn't afford to get him actual cat food.
In the novelization of "FLCLimax", as Mamimi searched the riverbed for Takkun, it was revealed that Eri Ninamori was now taking care of the cat and vowed that the high schooler will never find him. Ninamori then explains that during the previous week, she had found Takkun freezing in the rain. She had noted that Takkun had injured one of his legs, his skinny frame was convulsing and that he was too weak to even meow. After realizing that the cat was the one that Mamimi had been carrying around with her, she became angry that the high schooler would be that careless to let a pet suffer like that. As she continued to watch Mamimi search in the rain for Takkun, Ninamori whispered to herself that Mamimi will never find the cat, because it is now at the Ninamori residence and that she should learn to do things properly if she ever gets a pet again. Later in the novel, Mamimi confirmed that she wanted to adopt him but could not due to where her family lived. After searching in the rain for him for over two hours, she eventually gave up, hoping that someone would have adopted him, before finally realizing that she is all alone now.