You know how a continuous story that makes sense works? It has something happen, then it has something else happen that directly follows the first event, and so on and so forth. It’s the same with themes, where today’s thematic discussion has to correspond with and grow out of yesterday’s, for the story to make sense as a whole.
So, where are we in terms of themes with the show? Episodes 5 and especially episode 6 were all about trust. Episode 6 also introduced the “What would a superhero do?” style of thinking, that led to episode 7 revolving around being a superhero, about being naive. And while episode 8 last week seemed like it wasn’t all too thematically relevant, and served mostly as a break within the story, it actually drove home that Satoru is complacent, that he cares a bit more about being recognized as a superhero than being one, truly.
So how did this episode work to gather all these threads together in a meaningful way, how did it make use of past events? Well, let’s run down the list. First of all, it made use of Airi speaking of trust, actively bringing it up with relation to Kenya, to tell us an important message – people not only want to be trusted, but they want to trust others. When people aren’t trusted, they lose the ability to trust others, so they end up alone, as adult Satoru did. Child Satoru misplaced his trust, either in Yuuki, or in his mother and the police, so how could he keep trusting afterwards? And as he couldn’t, he withdrew from everyone.
But more than that, this episode kept revolving around superheroes, as Kenya and Sensei brought it up themselves.This is the true reward Satoru wanted all along, and also the reward he sought all the times he acted and saved people up to now – it was to see himself as a superhero. Of course, he also wanted to be seen as such by other people, which was a bit harder if they didn’t know he saved them, but that’s his first real interaction with Airi, and what got the series started – him saving people and being recognized and praised for it.
I mean, look at Satoru, he’s listening to his childhood’s favourite superhero’s theme song as he tries to think of how to save people next. And his conclusion? “I won’t let anyone alone again!” And if he truly means it, that he won’t letanyone be alone, then it’s impossible. There aren’t enough days in a millennium of years for him to keep up this promise. It’s a child’s wish.
And the episode ends where all stories must end, with a culmination of all plot-lines, with wrapping up all the themes together. There must be a balance that life demands in time-traveling stories such as this, right? More than that, there’s a balance in social interactions. Satoru had everyone trust Kayo, he had everyone not leave her alone. But in doing so he had everyone turn against another girl, mistrust her, and thus leave her alone.
Satoru said so himself, it’s dangerous to go beyond the map he had of past events, because he can’t tell how events will keep happening, but here he is, in a changed past, and he acts as if nothing will change further, while things changing are his goals. Naive. Naive dreams of being a superhero. But what can he do? I mean, for every action he does, for every person he saves, he just might be damning someone else, like the god of death from the story with Airi. He almost lost his mother then and there, in the past. What would he have done then?
Return to the Boku dake ga Inai Machi / ERASED Episodic Notes page.
Beyond the write-up above, I’ll outline a few shorter thoughts I’ve had during the episode to follow, but first, here is a screenshot album of more important moments and/or better-looking frames.
1) Satoru doesn’t understand Kayo as perfectly as he thinks he does. “Kayo isn’t moved by her mother’s self-pity,” he told us, but he forgot what his own mother told Kayo’s mother but moments earlier – that Kayo doesn’t want to see her mother like this either. Kayo may not understand and forgive, but just like last week with her deadpan face as she said she’ll be happy about leaving her house, it’s understandable that she’s of two minds about it – it’s still her mother and the only life she’s ever had.
2) About Kayo’s mother’s backstory. Didn’t make me care for her. I doubt it moved many people. It strove to make her understandable, and to show we’re all fallible people, I guess? But to me the main take-away was actually about Satoru’s mother – raising a child alone isn’t hard, and yet this mother succeeded, to a degree, as her child still ended emotionally stunted and shut away from society and human warmth. But still, that whole segment, it came far too late and did too little with a character who earned our distaste. I could’ve lived without it.
3) Yes, they want us to think of the teacher as suspicious, but man, I really smiled in this moment in the car. Supposing that he is indeed the murderer, as they keep trying to make us think, then they’ve made him human, and relatable, and believeable as a person. It’s everything they haven’t really done with Kayo’s mother. Because this form of characterization is based on a series of small moments, of touches and interactions, not by way of one big sob-story for a character we didn’t care for up to now and won’t meet from now on. I like the teacher. And indeed, asking advice from another single person, Satoru? Fat lot of good that will do you.
4) There was one thing that really stood out to me this episode. They went and hid Kayo in the bus, where the killer hid his stuff. The teacher pointed it out, that they hid her where only killers and kidnappers would go. And then we had Satoru tailing Aya, charting down her daily routine – just as the killer must have done. The latter is obvious for one who wishes to stop the killer, but combined with the first? It almost makes me wonder if true to time-travel stories, there’s another time-traveler here, a broken-future Satoru, or Kenya that got to be a superhero “just like Satoru”, because he too wanted to make the leap (time-leap?), who’s making the same choices as they, because he shares the basic personality of one of them (Edit: Though this doesn’t really fit the way time-travel works in the show, as bodies don’t go back, but maybe, somehow, something?).
5) Satoru asking for advice is sort of precious. He’s a 29 year old man asking his mother, and his teacher, both of whom are adults, on how to approach an 11 year old girl. How would they know? It’s the blind leading the deaf.
6) Some shots in this week’s episode weren’t as good-looking as in past episodes. Not all too noticeable, but even if the show didn’t try to paint Kayo’s mother as the bad guy here, it certainly painted her mouth badly ;-)
Return to the Boku dake ga Inai Machi / ERASED Episodic Notes page.
Geekorner-Geekulture. 
I really want you to be onto something with point number 4.
At least I believe that Satoru and the killer have a lot more in common than we know at this point. I don’t have a lot of evidence for that, just these screenshots from the op: https://imgur.com/a/uVolO
Notice how similar both Satoru and the killer are depicted in these shots and were the two of them are looking.
There was an omission that stood out to me here, that Satoru didn’t mention the mystery man’s appearance at the bus to his teacher even when the bus itself came up. There are reasons to actively hide that, since it would draw attention to how unsafe this plan of his had been in practice, but he was fine with bringing it up with his friends (who did already know, but didn’t have the perspective to know this likely was the serial killer). On one hand the kids aren’t able to punish Satoru, but on the other they don’t have the power to look further into this. Still, without a killer around there’s little reason to take this odd bus-frequenting person seriously, so I’m likely overthinking this.
I’ve suspected Kenya a little since the blatant foreshadowing of something more going on with him at the end of Episode 3, but him also time-travelling would be interesting (and explain his surprising maturity and genre savviness, notable even in Satoru’s memory). The presence of an adult that didn’t disturb Kayo but did reveal presence at the bus is a strike against this as it doesn’t make much sense if Kenya is in on it. I’m also curious about whether child-Satoru already relived these events once, with a Revival striking during the original series of events; the focus on him saying “I could have saved her” around the police interviews supports this.
My usual remark about scenes like Kayo’s mother’s backstory is “That explains it, but doesn’t excuse it.” Time travel is all about reliving cycles and figuring out what is or isn’t inevitable, so there’s a neat parallel here with a cycle of abuse that couldn’t end well due to lack of external support. I did like that the one way to stop this monster was to bring her mother, that even the abusive wreck felt guilt once her mom was watching.