The current brouhaha over the Rising of the Shield Hero anime is so depressing. People on both sides of the debate are taking the story at face value, and thus missing out on the deeper meaning of the series. Aneko Yusagi is a highly complex writer, perhaps even on the level of Gene Wolfe or Bret Easton Ellis, and yet people are treating his work like he's writing some simplistic story.
The first thing you must realize about Shield Hero is that Naofumi is an unreliable narrator. You can see this in almost any chapter. No matter what goes wrong for Naofumi, he always finds a way to blame someone else for his hardships; and when something good happens to him, he treats it as the world giving him his just rewards, even when he has done nothing to deserve such a reward--and even when we've seen him bully that reward out of someone. The only way the author could intend for this to be taken at face value is if he's an utter incompetent writing a straight-forward wish-fulfillment fantasy. Since this clearly cannot be the case, we have to dive deeper to understand what's going on.
Our first clue that something's up comes during the prologue, when we get a glimpse of Naofumi's life pre-summoning. He tells us right off the bat that he somehow "saved" his brother from going down a bad path in life, and in thanks his parents are not only letting him live at home while he attends college, but they're also providing him with an allowance--which he uses to live a lazy otaku life. But, he hastens to add, he's not one of those stinking hikikomori.
There are several reasons to be suspicious here. First, Naofumi never again talks about his family or expresses a desire to get back to them. It's only when things fall apart for him in Melromarc that he expresses any desire to go home, and even that is very general, without a specific mention to his family. If he had a happy home life, you'd expect that to be his top priority from the get-go. Other isekai deal with this issue either by making their protagonists some sad sack who has nothing to go back to, as with Overlord, or by having them die before being reborn in a new world, such as Konosuba. Yusagi does neither, which tells us Naofumi must not have anything he wants to get back to.
Now consider what we actually see of his life before summoning. He wakes up in a dark bedroom late in the morning, or possibly even in the afternoon. When he opens his curtain, he reacts to the sun almost like a vampire.
When he leaves the house, he doesn't speak with any family members, not even calling out "Ittekimasu". He wanders through the city alone before ending up at the library. The closest he comes to interacting with anyone is when he stops to stare at a trio of passing girls.
No wonder he insists upon telling us he isn't a hikikomori. If you've read Saitou Tamaki's book, Hikikomori: Adolescence Without End, you'll recognize much of what he describes in Naofumi. Japanese parents are often embarrassed by hikikomori and let them stay holed-up in their bedrooms, or even provide them with a separate apartment, rather than address the problem. Then the way Naofumi looks after those girls as they whisper to each other suggests internal anxiety as he wonders whether they're making fun of him, which is one of the classic symtoms of a hikikomori.
Yes, Naofumi does manage to venture outside, but of course so does any hikikomori who lives by themselves. Welcome to the NHK has long sections devoted to Satou struggling to go down to the convenience store so he can eat. And Naofumi's choice of where to go--a library--is the sort of space a hikikomori would feel safe in--dim and quiet, with tall shelves blocking him from the view of other patrons. If the library has a self-check option, he wouldn't even have to interact with a librarian.
We also get a clue later that Naofumi is lying about being a college student--or if he is one, that he isn't attending class--when he apologizes to the other heroes for being uneducated.
Now consider the story of why Naofumi says his parents let him be this way. He claims his brother started hanging out with a bad crowd, but he managed to pull him back in time. This clearly tells us that there's more to Naofumi than the rather wimpy guy he appears to be. The Naofumi we see in the first half of the episode is soft-spoken, barely able to do more than mumble in conversation, which is exactly what you'd expect from a hikikomori based upon stereotypes, but once he's accused of raping Myne, he flies into a screaming rage. According to Saitou's book, this is consistent with how hikikomori act. One reasons parents are reluctant to address the issue is that the child will become violent when confronted, which gives us an alternate explanation for why Naofumi is able to get away with what he does.
Which brings us to Naofumi's behavior in the other world. He's been pushed out of his element and forced to interact with other people. Unsurprisingly, he doesn't handle it well. From the start, he puts himself apart from the other heroes, standing to the side, lagging behind them when they walk. He can't bring himself to be part of the group. The Melromarcians pick up on this and try to give him space, but that feeds into his social anxiety. Just as he thought the girls in Tokyo were laughing about him, he assumes he's being singled out. Even if he hates attention, seeing other people get it while he's ignored just makes him more insecure.
Things get worse when it comes time to form parties. When Naofumi's introduced to his potential party mates, he simply stares at them coldly. His eyes are drawn instantly to Myne--not because she looks like a good fighter or anything, but simply because she's pretty. He ogles her.
She catches the look and returns it with nervous apprehension. She already senses this guy is bad news, and she's already trying to figure out how to defuse the situation.
Unfortunately, the other potential party members pick up on the feeling and none of them want to join Naofumi either. This intensifies the feed-back loop, as Naofumi feels like the kid in elementary school that no one wants to sit next to.
Finally Myne, despite her better judgement, decides to have pity on him, and offers to be his partner. Sadly for her, Naofumi misinterprets this act of kindness. Rather than think of Myne as a comrade in arms, he begins looking at her as a piece of meat. He acts ostensibly nice, but his mind has already gone elsewhere.
At the same time this is going on, Naofumi and Myne set out to buy equipment. Now mind you, the King just gave Naofumi a hefty war-chest--more than any other heroes--but Naofumi insists upon making ridiculous demands upon merchants.
This gets even worse later. After seeing an adventurer sell a pair of well preserved monster skins for one copper, Naofumi demands the same price for a pile of tattered hides, then, when the merchant refuses, attacks him.
Although Naofumi criticizes the other heroes for treating everything like a videogame, the fact is he's doing even worse--he accepts these are real people, and he's still trying to screw them over.
And the most egregious example of this is the incident that makes him persona non grata in Melromarc.
After their first day adventuring, Naofumi and Myne take dinner at an inn and discuss what to do next--or at least Myne does. Naofumi, believing that girls are never nice to guys unless they're attracted to them, spends the meal ogling Myne's chest.
He begins to perceive even the simplest motion, like sipping wine, through an erotic lens, and interprets a simple offer of a drink as an attempt at seduction.
Becoming overwhelmed by these ideas, Naofumi retires upstairs, ostensibly to go to bed. The scene fades out, and when we come back it's the next morning. Soldiers rush into the inn to arrest Naofumi for rape. Naofumi of course protests his innocence, but at this point it should be clear to any but the dullest audience member that he is not a reliable narrator. He skipped over everything that happened in the night to give the audience the impression that nothing has happened, but as anyone familiar with Japanese mysteries will tell you, this is clear misdirection. Examples abound where an author tricks the reader into believing the narrator is innocent of a crime simply by skipping that bit. Yukito Ayatsuji is particularly fond of the technique, using it outright in The Decagon House Murders, and a variation in Another.
So the truth of the matter is, while on the surface Rising of the Shield Hero appears to be yet another generic-ass isekai, it is actually a deconstruction of the genre, taking its cue from Stephen Donaldson's infamous Thomas Covenant, Unbeliever series. Rather than a leper like Covenant, Naofumi is an hikikomori who is driven to utter villainy by his inability to handle the social pressures of being a summoned hero.
Which is why at the end of the episode, having been outed for what he really is, he stumbles into a back alley, where a shady man dressed as a cross between the Penguin and Huggy Bear offers to sell him a slave.
Here is the final turning point, and Naofumi gives in utterly. He goes into the alley, fully intent upon buying a slave to fight for him. From here on out, he's going to be the villain of the story, even if he tries to convince the audience that he's the hero.