Aya and Chisato are members of the same band, Pastel✽Palettes; Aya is their vocalist, while Chisato is their bassist. Both of them are third-year students, go to Hanasakigawa Girls' High School, and are in the same class. The two have opposite personalities: Aya is bubbly, sentimental, easily cries, and a dreamer. Meanwhile Chisato is more calculated and professional, knows how to keep her emotions in check, and a realist. Due to their opposite ideals and personalities, the two clashed multiple times in the beginning. Chisato also tends to scold Aya sometimes and remind her to not do certain things (such as staying up late, or eating too many sweets).
Though Aya had heard of Chisato before, as she is a famous ex-child actress, and was a member of the same agency, the two met for the first time when their agency called them for an emergency meeting in their First Band Story. During the meeting they revealed that the four of them - Aya, Hina Hikawa who passed the audition, Chisato, and the model Eve Wakamiya - were going to form Pastel✽Palettes, an idol ban. However, the band has a twist: they are only going to pretend to play their instruments and lip sync while onstage. While both Aya and Eve were against the idea, Chisato quickly accepted it, saying how nobody comes to see idols for their musical talent, but rather for their appearance and personalities. This especially saddens Aya - who had been a trainee idol for three years - because she thought she was going to finally get to make her debut as a real idol.
With a concert scheduled two weeks later, the girls kept practicing and Maya Yamato, who was initially chosen to be just their support drummer until they found someone else, was announced to be their fifth member. When the day of their first concert comes in Chapter 4, the girls are pumped up to perform and start "playing" their first song; however, a major equipment problem happens in front of their audience of 10,000 people, exposing that their band is nothing more than a scam. Both the show and all their upcoming appearances get cancelled, and right after Chisato starts wondering whether she can stay in the band, as she believes that the band has completely failed and has no future at all, not to mention the scandal could tarnish her image.
While the other members keep practicing more than ever, Chisato only shows up to the mandatory lessons, and keep them worried. Secretly Chisato goes to ask the agency staff if she could quit the band. However, the agency staff denies her request, and tells her that leaving the band would most likely cause extreme backlash toward her, and they couldn't be able to protect her then, leaving Chisato to just bitterly accepting the fact she won't be able to escape. After the agency manages to schedule another concert for the girls, Aya expresses that she's happy because their hard work has been acknowledged and finally paid off. Chisato, in retaliation, asks her if it was truly was all thanks to her hard work, why didn't she debut as an idol earlier? This leads to Aya getting depressed and Chisato leaves. Later on, Aya and the other girls try their best to sell tickets to their upcoming concert outside. However, it starts heavily raining all of a sudden, and Aya stays behind despite this. After Chisato hears about this, she gets amazed over how stubborn Aya is, and goes to help her out, which leads to the starting to get along better. Chisato also starts reacting coldly to people who say how Pastel✽Palettes wouldn't operate as well without Chisato in it, or implying that nobody would care about the band if Chisato wasn't a member.
In "When the Flowers Bloom" event, Chisato gets called in by the agency who tell her a famous director named Takayuki Miyagawa has requested her for his upcoming play. Chisato is surprised, and accepts the offer as she imagines it could lead to her advancing even further with her acting career. When the girls hear about this, Aya remarks just how amazing it is for Chisato get requested by him, and then tells her that she's always ready to help her out. When the rehearsals start two weeks later, Chisato finds herself stressed out when Miyagawa keeps interrupting her performance and asking if she's even truly trying, or whether she knows what passion is. When the band watches her practice, Aya realizes that something is wrong with Chisato, but can't exactly pinpoint what it is. During a break they go and tell Chisato that she shouldn't worry too much and how she's a pro, so she'll definitely be fine. However, when Hina says that Chisato can do anything, it causes her to explode at the other members and telling them to get out. Later on the band realizes that Chisato was struggling and they were in the wrong for expecting that she's perfect and naturally good at acting, and how they didn't think that she'd worked really hard behind the scenes. In Chapter 4, Chisato talks to Kanon about what happened, which in turn makes her realize that despite their words, the other Pastel*Palettes members were trying their best to support her, and in Chapter 5, confesses to the other four that she is really bad at asking for help; the five then go to a cafe and Chisato shares more things about herself. A month later, their rehearsals for the play is over and Aya is the first one to tell Chisato that she couldn't stop crying while watching the play, which ended up being a success. After Chisato talks to Miyagawa about why she was chosen, Aya suggests they all take a selfie together. After they took it, Chisato remarks that she will use it as her screensaver.
In the event "Play Act! Challenge*Audition", both Aya and Chisato are called to audition for the same role for an upcoming play. The two keep cheering each other up while practicing hard for the audition, and Aya gives more insight on emotions to Chisato, as well as teaching just how the work "good luck" can be used in multiple ways. The two also end up being able to communicate just through winks and keep telling each other to do their best.
Ayachisa is not only one of the most popular ships in both the Eastern and Western fandoms, but also both Aya and Chisato's most popular ship. It is mostly seen as a pure and wholesome ship, though some initially disliked it because they saw Chisato as a cold character.
- So far the two have had three 4★ card pairs (the only other ship that has the same amount is Kasurimi).