A Certain Day of Summer is a Persona 3 Original Drama CD taking place in the Persona series. The CD consists of four short episodes, framed by Igor and Elizabeth as story-tellers. It takes place shortly after SEES returns from Yakushima. In the CD, the protagonist is always described as "him" or "you," and has no name given.
- Japan: April 25, 2007
A Certain Day of Summer begins with the protagonist being summoned to The Velvet Room. Igor offers to tell him about memories of past and forgotten events. Igor begins by telling a story about a man who dreamed of becoming a butterfly and enjoying flying freely in the skies. After waking, the man wondered if he dreamed of being the butterfly or if the butterfly was dreaming of being him. Igor explains that this man did not know everything about himself, yet he still awakened from dreams.
She Goes for a Walk (Tracks 1-3)
The story begins during the heat of summer after SEES returns from Yakushima. Shuji Ikutsuki is at the Dorm to ask everyone to take Aigis around town so she could experience things for herself. Akihiko and Mitsuru already have plans, so the protagonist, Yukari, Junpei and Fuuka are going out with her. Before going out on the town, they decide to dress Aigis up. Fuuka offers some of her clothing, but Fuuka is shorter and smaller than Aigis, so they don't fit. Yukari's clothing don't fit quite right either. Mitsuru offers some of her clothing as well, but Aigis says Yukari's are the better fit. Aigis prepares to reveal every difference between their measurements, but Yukari panics and manages to quiet her down before the secrets are revealed.
Yukari, Junpei, the protagonist, and Fuuka all take Aigis to Gekkoukan High School. While on the train, everyone tries to explain exactly what a school is, but it only serves to confuse Aigis. While talking about giving Aigis a tour, Yukari remembers the protagonist arriving as a transfer student. Junpei remembers being surprised that Yukari and the protagonist came to school together at that time. Fuuka remembers a lot of male students discussing the topic on the school message boards. Yukari is embarrassed and doesn't want classmates talking about her at all. Junpei believes it's good that she's so popular, and Aigis takes note of this fact. Junpei comments about how different things are and says encounters can be important and life altering. Aigis comments that first contacts are important, like battles. Yukari asks Junpei about why Aigis acted so strangely on Yakushima. Despite Junpei trying to hide it, Aigis reveals the way Junpei greeted her the first time. Yukari realizes that Junpei was trying to hit on Aigis, and Yukari laughs at him.
Once the group arrives at the school, they visit key locations around the building, such as the classrooms, student council room, and the PA room. Aigis breaks into a cupboard of strange CDs, a reference to one of Elizabeth's requests. Junpei wants to play them, but Yukari and Fuuka are afraid of getting in trouble. As they explore the school they encounter a note left by Bebe in French. Aigis translates and says that it warns against eating an item labeled "2-E" in the refrigerator. The note appeared to be unfinished. Junpei comments about how it must be a joke, but Fuuka looks disturbed. Aigis asks if she's okay, and Fuuka says she's fine.
Reverse or Broken? (Track 4)
Told through a series of phone calls, this segment focuses on the strong reactions of Yukari, Fuuka, and Mitsuru in finding out the protagonist has double-booked in his plans for a certain Sunday. It draws to a conclusion as Aigis decides to eliminate the cause of the disruption in the dorm by eliminating the protagonist. He awakens to discover he was simply having a nightmare, but collapses in terror after hearing his phone ring.
Noble Empress (Track 5)
Introduced by Elizabeth, this section of the disc is focused on a short story about Mitsuru reflecting on memories of her father. Interaction is primarily that between her and her staff.
Equip with Chidori (Track 6)
This final segment focuses on Junpei's relationship with Chidori Yoshino, in which he pesters her to let him have a piece of her art to show to others. Unfortunately, it is poorly received by SEES and he is at a loss to find someone who appreciates it as much as he does. Seeking Ikutsuki's advice on how to share her artwork with a wider audience, Junpei decides to print it on a t-shirt, which he intends to wear around town and while fighting shadows. The t-shirt agitates the shadows, but due to them focusing specifically on attacking Junpei, SEES decides that this could be helpful. It ends as Junpei ponders if he will manage to come back alive thanks to this.
Artist Segami Daisuke(a.k.a. "Daichou24") provided video versions of several portions of the drama CD, with humorous illustrations and animations cued to the dialog. These videos are available with subtitles on Youtube.