Throughout the series, Ayumi displayed a very cheerful personality. She gets along easily with other people, as seen when she first met Nao Tomori and Yū in her new apartment. She cares a lot for her brother, making sure to wake him up early to prepare breakfast for him every day. Ayumi gets excited easily, and tends to get nosebleeds at the sight or mention of Yusa Nishimori. She refers to herself as "Ayu" and is shown to be much more talented at cooking than Yu.
Ayumi doesn't know about the existence of abilities, and when Yū isn't at home, she thinks he's busy with the student council.
After a few episodes, she mentions that a boy had asked her out and she declined.
She then catches a cold and has to rest. Her friends come visit her, but Yū tells her to rest a second day, however Ayumi doesn't want to skip school, so she sneaks out and goes to school behind Yū's back. Yū and the others find out that she has an ability and went to quarantine her as soon as possible. Ayumi at the same time gets threatened by one of her classmates with a box cutter and the fear causes her to activate her ability of "collapse". The school building crashes and Ayumi perishes as her brother arrives at the school.
In Plunder, however, Yū travels back in time to save Ayumi, using Yū's "looted" ability from Shunsuke of time leaping and hiding in a metal maintenance cabinet on the top floor of the building so that he can emerge quickly to save Ayumi.
Ayumi is able to use the " collapse" ability which allows her to make objects around her to crumble and break apart; it is not to be confused with the power to generate earthquakes, as it doesn't seem she can emit tremors on ground. Her hair glows right before she activates her ability. She first (and supposedly, only) used this ability when Konishi, one of her classmates, was about to hurt her with a box cutter. But due to that, the entire building collapsed on her which led to her death. Yū was also caught up in the aftermath of the ' collapse' while trying to save Ayumi, though Yū survived the collapse. However, in Plunder, she is rescued by Yū by using his newfound Time Leap ability. Now Yū has her ability because he used his looting ability on her.
- She adds pizza sauce to every dish to help remind Yu of their mother. It is also likely Maeda's reoccurring theme of the family "bad food/sauce" seen in Clannad and Kanon
- She often gets nosebleeds when overly excited.
- After her death in Happiness You Did Not Notice, she made an appearance in The World that is No Longer Here, in a flashback
- She came back in Plunder, since Yū and the others managed to use Yū's looted ability of time leaping
- She is a very big fan of Yusa Nishimori and the band How-Low-Hello, or Haro-Haro.
|Main Characters||Yū Otosaka • Nao Tomori • Jōjirō Takajō • Yusa Nishimori • Misa Kurobane • Ayumi Otosaka • Shunsuke Otosaka • Takehito Kumagami|
|Supporting Characters||Maedomari • Medoki • Shichino • Furuki • Sala Shane • Kazuki Tomori • Yumi Shirayanagi • Tsutsumiuchi • Konishi • Udō • Arifumi Fukuyama • Saitō • Iori Sekiguchi|
|Minor Characters||Mishima • Kōta • Shō • Nomura • Oikawa • Sugimoto • Takato • Yoshiyuki Ōmura • Mrs. Tomori • Gondō • Hosoyamada • Mr. Kurobane • Mrs. Tomori • Honoka|