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Just one, but it's a big one: what does everyone have against this guy? Everyone despises him right from the beginning, no exceptions. Why?
They don't really have anything against him personally. Everybody hates him because he's the Shield Hero. The Shield Hero has historically always been loved and worshipped as the personal hero of demi-humans, whom everybody in that specific kingdom hates with a burning passion. So since he's the Shield Hero, they want to do everything they can to ruin him... and in the process are turning him into the very hero of demi-humans they want to prevent.
Read the manga or the LN. There are some characters that hate him because they're projecting their hatred of demi-humans onto the figure of the Shield Hero. Others hate him because of the political reason mentioned above.
To add on to all the previous reasons mentioned, he was accused of raping the princess...in a matriarchy. That's probably the worst sin you could commit there. She lied, of course, but the King was predisposed to both believing his daughter AND hating the Shield Hero for his own reasons, so he effectively turned the whole kingdom against the guy.
Um... what happened to Bow Bros and Sword Bros parties? It looks like only Spear Bro and Shield Bro kept their people alive.
It's said that you need all four heroes to stop the Waves, so what was the plan if the king or the church HAD killed the Shield Hero? The only way to summon another shield hero would be to kill all the other heroes and then you're back in the same spot.
Wait a minute, you mean to tell me that the Bow Hero brings down a corrupt government but he never even bothered to check up on them to see if they're alright? In fact, why did none of the other heroes (except Naofumi) ever check up on their good deeds?
They were thoughtless and selfish, not to mention that they are operating on video game logic — aka "everything resolves itself once the mission is over". To their credit, Ren and Itsuki do regret their failure after it's pointed out to them.
Naofumi's shield can change forms and powers. Won't that make it an overpowered weapon and yet it's looked down upon by humans?
Weirder still: if you use plain ol mmorpg logic, hes the ONLY tank, and (maybe) healer. Everyone else is DPS. They should be throwing themselves at his feet.
Remember that the Legendary Heroes only fight side by side during Waves. Otherwise being near each other negates any EXP gaining. They never have to party up for the majority of their time together, so they look to other party members for healers or tanks.
He has no real offensive ability (at first), so he has to rely on counter-attacks and more indirect methods. He might seem useless in fights, but those who underestimate him often regret it later.
I understand Naofumi not wanting to form a relationship with Raphtalia because she was still just a child when he found her. However from another point of view, she did biologically mature, or is it because of Raphatalia's lack of mental maturation?
Naofumi might easily adapt to the rules of the current world when called for, but he draws the limit when it comes to legal ages. Even if Raphalia looks like a young adult, her "mind" is nowhere near her physical age. Hence why he'd rather wait until she's legal in "his" mind, after she's matured due to passage of time and actual life experiences.
He could be oblivious due to lingering trust issues. Or he could be refusing to pursue any relationships due to said trust issues in addition to the above.
In the web novel, he really is that dense. Motoyasu even calls him out on it in Chapter 100.
He also knows that he'll go back to his own world eventually, and there's no apparent way to take anyone with him. He wouldn't want any hearts broken when that time comes.
There's also the fact that he, in part, raised her after buying her as a slave. He might have some lingering paternal, feelings for Raphtalia and that becomes too much Squick for him to consider a romantic relationship for his surrogate daughter.
Nothing odd there. After all, "virgin" is also synonymous with "unmarried woman" in the eyes of a child or "untouched" by the eyes of religious beliefs. No wonder she believes what she believes about the misunderstanding mentioned above.
Why did the anime change Fitoria's threat to Naofumi? In episode 16, 17 and 18, Fitoria is criticizing Naofumi for not trying to make up with the other heroes. The anime plays it off like Naofumi, the victim of the situation, is the one solely at fault for the things that have happened to him. Yet this doesn't make sense as no one would bother to help Naofumi, never mind try to hear him out, and Fitoria should already know this as she knows that the Shield Hero is hated in Melromarc. For anyone who's read the LN or Manga, this interaction doesn't exist, instead it's just her demanding that Naofumi bury his grudges; unconcerned by what they were.
Of all the people they could've picked to wield the Spear, why did it have to be a gullible, stubbornly deluded, skirt-chasing imbecile like Motoyasu Kitamura, who believes women can't be wrong or evil and refuses to live outside his own little world!? Were they so desperate that they couldn't pick someone smarter or wiser!?
You're presuming that the summoners actually get to pick the candidates for the four weapons before summoning them. That said, the summoning ritual is practically a "gacha game" on a insane scale. You put the coin in and what you get is what you got.
Did I say "picked" and "pick?" I meant "gotten" and "get." Regardless even if this was the case couldn't the forces there invoked have exercised a some measure of scrutiny!? Surely those forces had the power to choose which dead people became which heroes, unless a certain "goddess" was deliberately meddling in affairs to her advantage. In which case I rescind my argument.
It's just another jab at the "Isekai"-genre in general. Considering how many of those protagonists have a tendency to be loners, losers, NEETs, otakus or people so bland and insignificant or plain insufferable that they need to enter a whole different universe just to stick out from the background, the selection process might go by the priority of "pick people that nobody will notice or miss in their original worlds". The poor selection of these four are just the testament on how poorly it would turn out to have these kind of people dragged into this kind of situation with four different heroes to further be deconstructed. The four types being The Anti-Hero (Naofumi), the Idiot Hero (Motoyasu), the Ideal Hero (Itsuki) and The Drifter (Ren) being deconstructed down to the core.