Shinichi takes Mayuko back to his house. He tries to get her to tell him what's wrong but all she says is "he's grabbing me, pulling at my hand, it hurts..." He asks her if the promise she'd made not to tell was with Takuma, and if her drawing has something to do with it as well. She starts to panic, and he decides to stop questioning her.

Mayuko wants to stay at Shinichi's place, because her family all seem to like Takuma and she says they'll be "on the same side" as him. Shinichi calls Akiko to say that Mayuko is with him, because she's scared to go back to them. Akiko asks him what has happened.

Meanwhile, Jun's gone back to Yohei, asking him where Mayuko and Takuma have gone. Yohei gives him a searching look, and asks if he really likes Takuma. Jun replies that Takuma's been really supportive of their family and has even offered to help out with his tuition if the need arises. Hearing this, Yohei then looks away...

Rina calls Shinichi to tell him she's gone to the "scene of the crime" and is meeting with the police who had been in charge of Takuma's case 18 years ago. Shinichi tells Rina that Mayuko seems to have recalled the incident with her drawing, and she's with him right now. Rina says she'll be back by tomorrow and will contact him if she discovers anything.

Shinichi goes into the bedroom where Mayuko is and she asks him to change his bedsheets. She then worries that she is always asking him for stuff and says that she doesn't want to trouble him but even though she wants to be more normal, there's a lot she can't do. Shinichi reassures her that it's ok.

Shinichi says to Mayuko that although she called him "Shinichi-san" in her email, he will always be "sensei" to her, and perhaps that's why they can laugh and have such a good time together. He says that after reading her email, it seemed like the burden inside him has lightened. Mayuko tells him that she now understands what loneliness is... and Shinichi replies that he does as well, and it is the same sort of loneliness that he'd felt before. He tells her not to worry and that she can stay with him and be safe. She reaches out and holds on to his coat-tails.

The next morning, Mayuko wakes up early and goes out to the living room where Shinichi is slumped over the computer table, still asleep. She wakes him up by pulling open the curtains and laughs at his messy hair.

At the Amemiya residence, Jun comes downstairs and asks his mom where Mayuko is, but Akiko covers for Mayuko (guess Shinichi has told her what has been happening recently) and says she's probably at Misaki's. He finds it a bit strange, saying that Mayuko doesn't like strange places and doesn't even adjust well to changes inside her own bedroom, and wonders if she has gone to Shinichi's place. Akiko tells him he should trust Mayuko.

Shinichi leaves for work, giving her a housekey and telling Mayuko to leave her mobile on and not to let anyone into the house. Mayuko starts to clean up Shinichi's place, and she suddenly gets a call from Jun, who finds outs that she is actually at Shinichi's.

Osata-sensei goes to check up on Yohei, and seeing Akiko there, tells her how he'd heard Shinichi was doing therapy for Mayuko. He says Shinichi was his junior in med school and praises him as a very giving person, and someone to be trusted. He also tells her that Shinichi has repeatedly gone to him to ask that he does his best for Yohei. Hearing this, Akiko is starting to realise they may have been wrong about Shinichi...

Shinichi is in Sakuma's office and they're discussing his findings on autism. Shinichi comments that autistic patients have different characters, but they share a common trait in wanting to be "normal". Sakuma says that it's because they want to integrate into normal society. But then Shinichi notes that in their quest to be normal, they increase the pressure on themselves and end up closing in on themselves more, so in one sense they're actually strengthening their individualism. Sakuma is impressed with his reasoning, and says that he should consider going back to his hometown, Hakodate, where one of his former professors is now heading a hospital and specialises in research on development disorders.

Meanwhile, Jun's gone to Shinichi's to take Mayuko home but Mayuko won't open the door for him at first. She does after ascertaining that he really is on "her side" and she tells him that she's recalled something about Takuma from her drawing. Jun is taken back to hear she is scared of Takuma and asks her what she remembers. She won't tell him but simply says that Takuma's not on their side. Jun finds it all ridiculous and tries to forcefully get her to leave with him, but she shuts the door in his face. Jun tries to convince her that Takuma's not a bad person, but Mayuko refuses to be persuaded.

Shinichi goes to Scoop, and Rina introduces him to the police inspector (Miyoji-san) in charge of Takuma's case before. Miyoji-san asks to see Mayuko's drawing, saying it may yield some clues to Takuma's crimes. Rina tells them what Takuma had told her earlier about his son's accident, and how Mayuko was present at the time, and that's why she would be scared when she was reminded of the incident through the drawing. But Rina says that she knows he lied to her, and passes her newly finished article to Shinichi, which exposes the crime that Takuma has committed 18 years ago. She says Mayuko had drawn what happened 18 years ago and it was not an accident.

Sakuma's showing Mayuko's drawings to Jun (I guess he went there to talk about his adoption and find out more about his sister...) and he sees the picture of them holding hands, saying it was when he first became part of their family. While Sakuma's attention was diverted, Jun notices the blacked-out drawing, and surreptitiously picks it up.

Shinichi arrives home to find his place cleaned up but he's clearly used to the mess and seems rather ill-at-ease in all the tidiness. He notices that Muki's picture is gone, and he asks Mayuko where it is. Mayuko has put it among her own things, and she gets the photo and gives it back to him, explaining that she wants to love the things that he loves and even if she doesn't understand want love really is, Muki's smile in the picture seems to be filled with love, and she also wants to not forget the things that he doesn't want to forget. Shinichi tells her that even though some things are unforgettable, he no longer finds them painful, and he hands her the photograph.

Shinichi suggests they go shop for food, and they have a great time at the supermarket. (There's this pretty funny scene where Mayuko selects a blue toothbrush but Shinichi tells her to choose a different one as he's using the same one right now in his home and they wouldn't be able to tell them apart. But she insists that she has to have a blue one, and makes him buy a pink one for himself!) As they walk home together, Akiko who was heading to Shinichi's, sees them from afar and realises how happy Mayuko is with Shinichi.

Rina goes to visit Yohei in the hospital and tells him that she's interviewing him for an article she's writing on Takuma's dirty past. She shows Yohei the latest copy of the Scoop magazine, and Jun, who's also there, takes it from her after he notices the cover teaser. Rina tells Yohei that she knows he used to live near Takuma, and he was first acquainted with him when Mayuko was three years old... Yohei starts to cough, and Jun goes out to get him some water, but stays outside the door, listening to their conversation. Rina continues on, saying that at that time, Takuma's relationship with his wife was not good, and they had a 3 year-old son and a newborn infant boy, but the elder son died in an "accident" except she suspects it was actually murder, and Mayuko was there at the time, as she had gone over to play. Rina asks if Jun is aware of what happened to the infant boy...

Mayuko's working on Shinichi's computer, and as he comes out into the living room, he comments on how hard-working she is. But she says that even though she's trying so hard with everything, she still isn't able to do the job that she wants to do because she is not able to understand what others are thinking, despite all that Shinichi's taught her. Shinichi tells her that she should not force to accept things just to be like other people ("gamanshinai itte ii"), and that she's fine as she is right now. He tells her that he doesn't want to be her teacher and teach her things anymore, and he just wants to be himself. He gets up, saying "sensei wa mou owari" (sensei is finished).

Mayuko tries mouthing the words "Shinichi-san" and then wonders what she should do from now on. He tells her that she should choose her own preferred lifestyle, just that he too has his own lifestyle. He makes her a "yakusoku" that he will protect her from now on... and he has once made this very important yakusoku but in the end he failed to fulfill his promise to protect the other person, but he thinks he has been forgiven for it. Because, he says, "yakusoku" is the trust that exists between two spirits ("shinji iru no tamashii") but the promise to protect someone is actually painful, and so it is not a real yakusoku.

Rina calls and Shinichi says that Mayuko is still holding fast to her promise not to tell... but Mayuko, who has been pondering on what Shinichi just told her, suddenly says that she will tell them what happened.

Jun takes the issue of Scoop to Takuma, asking him if it's true but Takuma just makes a comment about how industrious the reporters were even in those days. Jun asks if Mayuko really was a witness to the incident, and shows him Mayuko's drawing. Takuma takes it and rips it up, but as he's burning it, Rina walks in. She says that the drawing was really of him, and mentions the scar on his shoulder. She then tells him that his wife has agreed to be a witness for the prosecution. Mayuko and Shinichi comes into his office (wow, it's a regular party!) and she tells Takuma that she decided to break the promise even though it is deceitful, because it's Takuma that is doing the lying, not her. She says Takuma drowned his son and she saw him do it but he made her promise not to say anything, and at the time she also heard the sounds of a baby crying. Takuma says that her words alone are no proof, but Jun cuts in, urging him to tell the truth. Jun then asks Mayuko if the baby boy was himself. Mayuko recalls the sounds of crying, and says softly "Jun, don't cry..." Jun says that he believes his sister and so what she says must be true. He is Takuma's son.

Takuma decides it's not worth fighting any longer, and tells them that he had fallen into massive debt at the time, and decided the only way was his whole family to die, and so he'd drowned his son. But his wife ran off with their baby and he didn't know that she had actually taken him to Yohei's home. Takuma says that Mayuko's recollections are totally accurate, and that was what he'd feared most. Jun calls him selfish, and he agrees that he is a selfish father, but he just wanted Jun to have a good life growing up and that he didn't want the incident to come to light. He says that he knows he owes Jun a lot.

The police come in and put Takuma under arrest, saying his wife has come forward with the evidence. Miyoji-san goes up to Mayuko and says he hopes she will just wipe the disturbing incident from her memory. As Takuma leaves, he asks Jun to forgive him and Jun calls him "otoosan...", but then he says to Jun that it is Yohei who is his father.

Jun takes Mayuko home, telling Shinichi that despite everything that happened, he still can't forgive him. Shinichi says that he is no longer Mayuko's sensei, but Jun says that if he had never met Mayuko, none of this would have happened. She wouldn't have known of her autism, and she wouldn't have had the recollections. Shinichi says that even if Mayuko hadn't known she had autism, the truth would remain that she still wouldn't be Jun's real sister, and he says Jun should be able to understand how hard it is to be misunderstood by everyone. Jun leaves with Mayuko.

Rina then says to Shinichi that Mayuko's memory really helped to solve the case. Before walking off, she says that if Shinichi really cared about Mayuko, he should let her know.

Shinichi then starts running off after them, and when he reaches them, he tells Mayuko that he'll always be by her side and makes a yakusoku with her that he'll be there no matter what she chooses to do. Mayuko repeats, "...what I choose?..." ("watashi wa erubu...") and Shinichi says, yes, because he loves her. Even though she may not fully comprehend right now what love is, he knows that she will be able to understand it one day. Jun starts to lead Mayuko away, but she turns back to Shinichi and makes a yakusoku with him that she will find a way to discover the meaning of love...

(Mayuko's monologue: Summer solstice is the longest day in the year. The sun lingers with its warmth and light..... the warmth and light that is within me comes from my own sun. Even though the road ahead may be foggy and unclear, I will continue to seek out my way...)

Mayuko emails Shinichi, saying she'd been thinking over his words and what he'd said about how she was fine as she is right now and not to lose herself just to be like everyone else. But she's still not sure if after choosing her own way, Shinichi will still be with her.

Shinichi emails Mayuko back, telling her to always remember that "you are who you are". He says that while he's seeking out his own direction, he's also thinking about Mayuko's direction. He hopes that she will have the courage to face up to her own emotions, and that she will give careful consideration to her future direction.

In Mayuko's bedroom, she's working on her homepage while Misaki is doing some architectural drawings. When they've both finished, Misaski remarks that even if she doesn't know if she's any good at it, it is important to be able to pursue what one really wants. Mayuko then walk over to study her expressions diagram, telling Misaki that she really wants to be able to understand the feelings of other people. Misaki asks if it is because she wants to understand the feelings of the person she loves...