Ren Amaki/Relationships

Naofumi Iwatani
Ren initially holds a low opinion on Naofumi, considering him weak due to his Shield, and a horrible person due to the false rape accusation pressed against him. His opinion hasn't improved by the next time they meet, as he easily believes that Naofumi had stolen a job from him, however, the realization that he caused a disaster that Naofumi fixed left him shocked and guilty enough that he immediately ran off to investigate the matter himself.

By the time of the third Wave, Ren's opinion on Naofumi as a human being has improved, as he is the only one who doesn't berate Naofumi for joining in on the boss fight, and even follows his lead when he realizes how to draw out the boss. That said, he still attributes his Wrath Shield to a cheat. When Melty's life was in danger from The Church of the Three Heroes conspiracy, Ren was the first person willing to believe that Naofumi was innocent of trying to "harm" the princess, and had even apologized for doubting him when Malty had shown her real nature.

However, Ren grows both frustrated and jealous that Naofumi, who can only use a shield, is stronger than him, who uses a sword, to the point that when it comes for Naofumi's time to speak during the meeting of the Heroes, he easily joins in on accusing Naofumi of cheating. Following the Spirit Turtle's rampage, Ren becomes sympathetic to the plight Naofumi faced when he first came to Melromarc, as he now faces the same persecution at the hands of the same people.

That said, his depression leads him to trust Malty over Naofumi - that had proved to be a big mistake. When Ren falls under the influence of the Greed Series and Gluttony Series of his sword, he comes to see Naofumi only as a high-level boss with rare drops and a high EXP reward, and it takes Eclair Seaetto beating some sense into him to make him see differently.

Now purged of the negative aspects of his personality, Ren starts to see Naofumi as an unexpected source of wisdom, and comes to live under him in his village.

Itsuki Kawasumi
Ren and Itsuki appear to get along amiably. During their down time they are shown eating and talking together, and whenever Itsuki accuses Naofumi of cheating, Ren is quick to follow him. Ren was also able to persuade Itsuki to investigate into the charges against Naofumi.

Raphtalia
Ren did try to help Raphtalia when he believed that she was forced into slavery by Naofumi, though when he saw how close their relationship was, he was not happy about being duped.

Glass
Ren despises Glass, who openly mocks him as being too weak to be a Hero.

Aultcray Melromarc XXXII
Ren holds a slightly bad opinion of the King, while he never treated him as badly as Naofumi, he also didn't treat him as well as Motoyasu, and he also knows that Aultcray was bullying Naofumi by not giving him quests or making excuses to hold back his funding.

Welt, Bakta, Tersia, and Farrie (deceased)
Ren treated his former companions like members in a guild, assigning them areas to level in independently, and having them do errands for him. After they were killed by the Spirit Turtle, their deaths and the guilt he felt for them were enough to send him spiralling into depression. After being cured of his Curse Series, Ren comes to blame himself for their deaths, and seeks to save the world to honor their sacrifices.

Eclair Seaetto
Eclair and Ren initially have a bad relationship, stemming from Ren's belief that level is all that is important and that being a Hero automatically made him stronger and more skilled than her. When it comes time to snap Ren out of the Cursed Series, she is the one to volunteer to beat some sense into him, and ends up not only beating him twice, but also saving him from a pair of Reincarnated Individuals.

When Ren finally comes back to his senses, Eclair is assigned as his training partner and instructor in both the Hengen Musou style and proper swordsmanship.

Wyndia
Ren has a huge amount of guilt about Wyndia, as he is fully aware of the fact that her status as a orphan and a slave stems wholly from him murdering her father Gaelion, and seeks to make amends. Wyndia, for her part, hates Ren for murdering her father, though she isn't so petty to try and seek revenge on him, she tells him that if he wants forgiveness, then he should save the world.

Gaelion
Ren feels guilty for murdering the adult Gaelion, though he isn't aware of the details of his resurrection. The current Gaelion hates Ren to the point that he doesn't even want to let the Hero know that he's still alive.