Naofumi Iwatani/Relationships

Raphtalia
Naofumi's first slave that he bought from the Slave merchant. A Tanuki Demi-human. Naofumi bought her early on to compensate for his inability to attack and chose her both for her low price and because he wanted to imagine enslaving Malty. Despite his questionable reasons for buying her, Naofumi treats the growing child well, giving her medicine, food, and protects her during battle. The only times he ever activated the Slave Crest is when she's too scared to do it on her own. He also shelters her and comforts her during her various night terrors.

By the time she physically matures due to level grinding. One week later, Raphtalia becomes significantly more outgoing towards Naofumi and even has a decent handle on him, carefully findings ways to get him to comply with her choices despite their master-slave relationship. She becomes a much needed pillar of support for him; even willingly chooses to remain his slave, despite her new status as a free woman, all because of Malty's actions, Naofumi can't trust anyone who's not a slave.

She's the first person, after Oyaji, to take his side after what Malty did to him, and the one who ultimately succeeds in bringing him out of his despair. She want’s Naofumi to look at her as an adult woman, to the point where at least once she's stripped completely naked in front of him and asked him what his opinion of her naked body was, only for him to miss the point completely. The primary issue is that he knows that she's really ten years old despite looking like a twenty year old, and thus he doesn't think of her feelings as romantic.

Naofumi constantly believes they have a father-daughter relationship but Raphtalia would very much beg to differ. She's the one he trusts the most, and the one he ultimately cares for the most. Raphtalia is also the only real leash that's reliably restraining Naofumi's more villainous tenancies as she would prefer him to act as a prim and proper hero, which he doesn't think he is. Whenever Naofumi takes joy in the suffering of those who've caused him grief, especially Malty and Trash, Raphtalia tries to caution him against showing his joy.

For Naofumi Raphtalia is a reliable partner, she saved him from his hatred from being betrayed by Malty, and is his most loyal follower. She is the friend with whom they shared their joys and sorrows together.

Filo
Naofumi's second real comrade and slave. He bought her as an egg from the same slave trader that he got Raphtalia from and he raises her quite lovingly together with Raphtalia. She quickly grows beyond a normal Filolial and is revealed to be a Queen, and later demonstrates the ability to assume human form. When she kicks Motoyasu in the crotch during her first encounter with him, Naofumi immediately feels she was a brilliant investment and tells her to do it every time henceforth. After she started to assume human form, he has found her to be visibly annoying at times, especially for her selfishness and gluttony, but he still cares for her greatly. The moment he thought died was enough to invoke his Shield of Anger for the first real time since Raphtalia was nearly taken away from him.

Melty Melromarc
The Second Princess initially believed her father's lies about Naofumi and hated him, she attempted to make him apologize for dishonoring her father but was treated by him as an annoyance in return. After the Three Heroes Church tries to kill her, Naofumi becomes the only person Melty can actually rely on to save her life as the other heroes, her sister, and her knights are all either being used by the Church or are willing participants in the conspiracy. Because of this, she has become something of a Tsundere towards him, and it's implied that her feelings for him extend beyond what she wants him to hear about. She dislikes being treated by him as a child or being called "second-princess" by him, and gets him to call her by name instead.

Rishia
Recruited to Naofumi's party after being kicked out of Itsukis party. She was framed for breaking one of Itsuki's accessories by another member of the party. After Filo saved Rishia, Naofumi swear to make her stronger so Itsuki would beg to have her back on his team. As she spent time with Naofumi's village, she gained confidence and immense fighting skill. According to the Battle Instructor, her abilities are one that come every hundred years.

Amaki Ren
Like the other heroes, Ren was initially led to believe Naofumi guilty of the charge of raping Malty, however, he was also, alongside Itsuki, one of the only people to defend Naofumi when Malty cheated to allow Motoyasu to beat him in their dual. He is also the only one of the heroes to actually believe Naofumi when he is later charged with kidnapping Princess Melty and he denies it. Naofumi considers Ren something of a loner, who runs his party like a guild and acts on his own at most times. While it can be said Naofumi does not find him as unbearable as Motoyasu or Itsuki, he still displays petty dislike of him and even tried to kill him when he succumbed to the influence of his Curse Series weapons. He does however see Ren's good side as a hero, and defends him when criticized by Raphtalia's high standards.

Kawasumi Itsuki
Naofumi's relationship with Itsuki is strained to put it politely, he dislikes how Itsuki acts solely to flaunt his pride and show off, and, like the other heroes, is quite begrudged at Itsuki for believing Malty's frame up. Later on, he did defend Itsuki from Raphtalia's criticisms by stating that Itsuki was stuck up, but would never let harm befall his allies, however, what little respect he had for Itsuki completely disappears when Itsuki kicks Rishia out of his party for being weak.

Kitamura Motoyasu
Initially Naofumi believed Motoyasu played a part in framing him for raping Malty, but over time has come to realize that Motoyasu is very stupid and evidently doesn't know he's being manipulated by Malty. It was Motoyasu nearly taking Raphtalia away from him through a rigged duel which finally set Naofumi off enough to awaken the Shield of Wrath. Motoyasu tries to behave in a friendly manner towards Naofumi, despite the charges placed on him, but becomes something of a rival to him, especially with Malty's continued influence upon him. Once Naofumi's name is cleared he begins to show more of a kind side towards him, but refuses to accept it when he's told that Malty is the one who set him up. After Malty finally betrays him as well, Motoyasu completely breaks, falls completely in love(or lust) with Filo, and starts calling Naofumi Father in Law. He becomes even easier for Naofumi to manipulate, and all but swears loyalty to him.

Aultcray Melromarc XXXII (Trash)
Naofumi hates the king, and with good reason. With his daughter Malty, the king set Naofumi up as a criminal with the charge of rape and spread the word all over his kingdom. However, given his genuine display of stupidity in believing the claims that Naofumi could brainwash people, it's also likely he just believed Malty's claims. Ultimately, the king hates the Hero of the Shield, and that just unfortunately happened to be Naofumi. When the Queen cleared Naofumi's name and allowed him to punish the king, Naofumi immediately asked for the death penalty, but was talked down to renaming the king to "Trash" and stripping him of all his rights to the throne.

Glass
Glass seems to consider Naofumi and his party to be worthy opponents, even asking for his name after he manages to force her to retreat during their battle(for reference, she moments before defeated the other three heroes and their respective parties, all of which are groups larger than Naofumi's party, at the same time). Like many others she finds some clear fault with Naofumi's personality.

Mirelia Q Melromarc
The queen and Naofumi are on fairly good terms as business acquaintances go. While he knows he's being used by her, he also knows that she needs him, so he's willing to put up with it. The fact she cleared his name and punished her husband and daughter for their mistreatment of him seems to be the crux of their relationship. Mutually benefiting off of one another, Naofumi and Mirelia have a business like relationship.

Elhart
He runs a weapon shop in Melromarc. The only person who believed in Naofumi after he was falsely accused by Bitch. He made most if not all of the equipment worn by Naofumi as well as his carriage. Also responsible for teaching Raphtalia the basics of Swordsmanship. His skills come from a blacksmith from the east. He wants Naofumi to find another blacksmith as he believes his skill to be sub-par.

Slave Merchant
While Naofumi considers the Merchant to be a useful ally due to his role in providing him various slaves for his growing army, he does not per say trust the man. The merchant has noted that Naofumi has good business sense, and is not an easy man to deceive, he refers to Naofumi as his favorite customer.

Malty Melromarc
Naofumi hates Malty for setting him up for the crime of raping her, this hatred grows exponentially over the series as Malty continues to antagonize him and try to add to the misery she'd already made his life into. After Malty's mother,the Queen, clears Naofumi's name and strips Malty of her right to inherit the throne as punishment for her actions, he immediately asked that she be executed, but was talked down to renaming her "Bitch" and later "Witch" instead. Malty remains utterly unrepentant for her past actions and aims to do whatever she can to get back at Naofumi.