After the obligatory previous episode flashback, we see Rei sitting on the beach as the sun rises, wondering why Fukiko loathes the song she played.
Nanako calls Rei's apartment from a payphone (oho, how quaint) on the way to school, only catching the train because Tomoko points out she'll be late if she doesn't move it. Nanako called before and never got an answer, so she figures out that Rei never returned home last night. She notes that she is rather scared of the insulated little world Fukiko and Rei are in, from what little she knows of it.
Despite catching the train, Nanako and Tomoko miss the bus, and I remember how much of a bitch Japanese high school commutes can be. (I did some study abroad there in high school.)
Pulling his car out of his university's parking lot, Takashi sees Rei, and she gets in the car. She plays a CD with the song Fukiko hates, stirring my nostalgia as a 24-year-old old person. Takashi is then like "So, uh, I guess yesterday's still bothering you." Rei explains that she figures he might know something about why Fukiko acted the way she did, and they go to the ocean so they can enjoy the salty sea air while Takashi explains his version of the most awkward backstory ever.
Six years ago, Takehiko visited the Ichinomiya summer villa for a week. The Ichinomiyas had their usual end-of-summer party coming up after he left, so he said he would be back for it. Fukiko began practicing the now-hated violin piece with gusto.
Interesting use of the blacked-out face effect for Fukiko here. It's normally used when she has some malevolent intent -- though it was used on Rei when she tried to fulfill her and Fukiko's double suicide pact with imaginary Fukiko. You also may have noticed it, less prominently, on Rei in the music box screenshot above -- there, the blacked out faces serve to make them more doll-like, befitting the imagery around them. Regardless of the context in which blacked out faces are used on Fukiko and Rei, they serve to underline their respective unhealthy obsessions. In the case of the screenshot right above, the beginning of Fukiko's obsession with Takehiko.
Anyway, Fukiko did a fantastic job playing the piece at the party and her audience wanted an encore, but Takehiko wasn't there since he had to take care of an emergency, so no more violin.
Takashi just now mentions that he never heard Fukiko play that song after the party. Rei notes that she's seen Fukiko play it loads of times since then... but never with other people around.
Rei asks if Takehiko ever came back to the villa. Takashi says nope and connects the dots regarding Fukiko's obsession. Arriving home, Takashi sees Fukiko arranging red and white roses in a vase. Demonstrating amazing subtlety, he mentions that he and Rei chatted about that summer six years ago and Takehiko. Fukiko cuts a red rose in half and is like "WHOOPS, THIS ROSE IS RUINING THIS BOUQUET, THIS ENTIRE BOUQUET IS NO GOOD NOW" and tosses it in a trash can.
Meanwhile, poor Rei is talking to The Doll as a stand-in for Fukiko, apologizing for not knowing her feelings about the song. Even more than usual, she needs to get out of her apartment and go outside.
Still in her room, Fukiko reminisces about that summer, and we finally get her full take on it. Takashi first introduced Takehiko to her when they were vacationing at the villa. Fukiko was taken with Takehiko right away, even moreso when he saved her hat from a waterfall.
Sonnet 18 while remembering spending time with Takehiko.
Guess which one that is.
Takehiko read the poem every time she requested it, took her rowing on the lake, took her to a cabin to shelter her from the rain, and let her have his book since he thought she just really liked the sonnets when she memorized Sonnet 18.
My girlfriend Amy adds an excellent observation, which she's typing here: Fukiko's story is fascinating because she's a teenager looking back on when she was twelve the way you normally see some adults look back on their teen and childhood years, making her feel older than she is, in a way. Teens usually want to distance themselves from their younger selves, but in this case the sense of heightened reality in the story shifts the dichotomy from "adult and child" to "teen and... younger teen" and that makes the story feel more like it's for mature readers.
We see Nanako go to Rei's apartment to check up on her. The Doll and the violin CD are on the bedroom floor, and Nanako plays the CD in the stereo nearby. She recognizes the song, and finds this behind her.
Later outside, Nanako can clearly tell that Fukiko's issues with her aren't just about her visiting Rei, and that the song has to do with it.
Later while being driven, Fukiko ponders what a tragedy that day was
She tries to drown herself in the lake, but floats up and cries on the dock. Back in the present, we see that she views what happened that day as a betrayal, despite her still wanting Takehiko and seeing that time before the concert as the happiest of her life. She is then like
So, um, yup. That was a backstory. When I first watched this, I was like "What the fuck, what a stupid thing to try to drown yourself over." It is still a picayune reason for attempting to drown oneself, but I guess... in the larger context of Fukiko's making-a-mountain-out-of-a-molehill behavior, it's in character. And what Amy said above, regarding what seems to be the intent of this plot point.
Between what we've seen regarding Fukiko's obsession with Takehiko and her willingness to commit suicide with Rei when they were younger... yeah, her time with her crush aside, she hasn't been happy in a long time. Rei's issues can be easily explained by the way her mom died (which I won't spoil) and the fact that her remaining family treats her like an embarrassing secret. Fukiko is harder to quickly explain because she has grown up taken care of way more than Rei. Clearly because of Rei's existence, which she knew about before the events of that summer, she knew her dad had a mistress, the same reason Mariko acted out until Nanako was like "Holy shit, your behavior." And from what I remember, despite numerous scenes taking place in Fukiko's home, we never see either of her parents, unlike Nanako's very involved parents and Mariko's mom who's trying to provide the most stable family she can for her daughter. So... I assume her latching onto Takehiko's willingness to spend time with her may have been caused by loneliness related to that. If I think about it, I can see reason for her behavior, however overblown and destructive.
On that delightful note, next time on Oniisama E, Fukiko will try to seduce Nanako away from her non-relationship with Takehiko and Rei will come upon it. Nanako just can't win.