Natsuki Subaru/Relationships

Emilia
Subaru fell in love with her at first glance, largely due to her being the first one to show him kindness when he was transported to the new world. He devoted himself to protecting her no matter what happens to him, even if that meant having to repeatedly go back in time by dying. Initially, she didn't understand the meaning of his playful flirting with her, but gradually she nevertheless developed reciprocal feelings for him and even became jealous if she saw his "interest" in other girls. Their relationship is one of the main themes of the series and, in fact, the main reason for Subaru's development as an individual, because thanks to her, he gradually got rid of his impulsive personality and learned to be more reliable, judicious and useful person than how he was at the beginning of the novel. Later Subaru officially became her knight which symbolizes the strong bond of trust she has developed towards him.

Satella
Satella is the one who granted Subaru Return by Death and also stands behind his summoning to the new world. Originally, Subaru harboured intense hate and fear for the Witch but upon finally meeting her face to face in the Witches' Tea Party and coming to understand her intense emotions with the help of Carmilla's Authority of Lust, Subaru promised her that one day he'll find her and save her no matter what, despite Satella's initial request to kill her. In the prologue of the 9th volume, Subaru shows mutual and intense feelings for Satella which gradually turned into (and were described) as representing each of the seven deadly sins, starting from sloth and ending with jealousy.

As already mentioned, The Witch of Envy stands behind Subaru's Return by Death. Whenever Subaru breaks "their promise", Satella preforms some type of punishment, either by crushing his heart or (in extremely rare occasions), crushing the hearts of people he cares about the most. In arc 6, Satella repeatedly caused the destruction of the Pleiades Watchtower and killed everyone in it, as long as Louis Arneb was latched onto Subaru.

Puck
Subaru has a relatively positive friendship with Puck, likely stemming from the spirit's friendship with Emilia. However, in a loop where Subaru accidentally killed Emilia by telling her about Return by Death, Puck angrily froze him to death for breaking his promise with Emilia, returning to the mansion against her wishes, and being the one that killed her.

Felt
Subaru met Felt in the first loop when some thugs assaulted him but Felt didn't help. Later on, she was about to get killed by an assassin but got saved by Subaru. From there they both established a friendship. Sometime later, when they met again in the capital, Felt showed that she was still making fun of him. Despite the confidence they both have, Felt doesn't like to approach him.

Reinhard van Astrea
Upon first meeting Reinhard, Subaru immediately recognized him as someone who has been chosen by God himself. Originally jealous of his gallantry and manliness, Subaru did not waste much time and started his soon-to-be-necessary relationship with him on a good note. As it later turned out, Reinhard's presence was vital in overcoming the Loot House incident and defeating Elsa while saving Emilia's life and returning her stolen Insignia. Despite being better than Subaru in every way imaginable, Reinhard considered Subaru to be his equal; even more so after Subaru defeated the Hakugei, liberated the Sanctuary and played a vital part with retaking of the Watergate City of Priestella, having been the key card in taking out the Sin Archbishop of Greed.

Currently, both Reinhard and Subaru harbour immense respect towards each other, with both of them swearing to each other that they'll fill the other party's shortcomings; Reinhard will play the role of a sword and Subaru will play the role of the tactician. They both consider each other as good and reliable friends.

Beatrice
Subaru and Beatrice initially had an antagonistic relationship. Subaru's personality often annoyed Beatrice, leading her to always mock and insult him. Subaru however began to rely on Beatrice for knowledge and advice and exclaimed how close they are. While Beatrice's actions had implied the friendship was one-sided, she did to an extent cared for Subaru as she cured him of his curse and foretold him about his death and how he could avoid it. She willingly made the contract to protect him from any potential threats to his life and defended him from Ram and Roswaal's attacks post Rem's death. After she became his Spirit partner, she started to open up to him.

Rem
After initially starting out on a bad foot, Rem eventually comes to fall for Subaru after he ends up emotionally and physically saving her during the events of the second arc, where afterwards she began devoting herself to him. After she confessed and won over a part of his heart after her numerous efforts to support him in the third arc. Subaru even agreed to take Rem as her second wife, but only if Emilia would allow it. In the fourth arc, he admitted to Emilia that both her and Rem are very precious to him, though Emilia still remains first for him. Subaru was heartbroken to discover that Rem had fallen into a hibernation-like state and that not even his Return by Death could save her. However, he pressed forward knowing that would have been what Rem would have wanted him to do and in the hope that he can one day free Rem from her slumber.

Ram
Ram has a rather amicable relationship with Subaru despite the constant disparaging remarks she throws at him. During his time as a butler, she was in charge of teaching him about their daily duties. She even took the time to teach him how to write so he became more accustomed to life at the manor. Ram was also the first person to vouch for his character when it came to the possibility of him being a spy even when his past was still virtually unknown. Despite harshly assessing his skills as a butler, she nevertheless held a sense of fondness for him as her junior colleague. Ram would later come to trust Subaru's intuition even if the likelihood of the scenario had no basis due to his unexpected successes. Although they both hardly mention it, they both care very much for each other's well-being and they are both good friends.

Roswaal L Mathers
Subaru was originally impressed by Roswaal, admiring him as the head of the Roswaal mansion and Emilia's primary benefactor despite the mage's eccentric behaviour. After the event of Arc 4, however, he realized that Roswaal is actually an egoistic and cruel person dedicated solely to reviving his master. Among Subaru's allies, he is the first to figure out that Subaru is looping through some method, though he never understood in what exact way. After Subaru defeated Roswaal in their challenge, Roswaal has agreed to help him but has also threatened to force Subaru into undergoing another loop if he makes a mistake.

Meili Portroute
Subaru and Meili first met during the time when she was disguised as a village girl. After Elsa Granhiert's death, Meili was captured and was locked up under the Miload mansion. Subaru forgave her and gave her a panda to convince her to help him out. During the events of the 6th Arc, the two of them grew closer and closer, to the point Subaru asked her if she'd join their camp. Meili views Subaru almost as an older brother.

Julius Juukulius
Subaru and Julius started with off on a bad note, due to Subaru rash acting at the Royal Selection and offending the whole Royal Knight garrison, which Julius was unable to accept. While both had apologized to each other after the battle with the Hakugei. Despite that, Subaru had told him that he still hated him, to which Julius stated that he didn't think they could be friends. After Julius' name got eaten by Roy Alphard, their relationship has gotten somewhat better and they both became close friends with a strong mutual liking and respect which was shown during their trip to the Pleiades Watchtower.

Crusch Karsten
Subaru has fostered a good alliance with Crusch after the success of killing the Hakugei, with Crusch even giving most of the credit of the victory to him. After her memories got eaten by Ley Batenkaitos their relationship became somewhat neutral. However, after the events in Arc 5 at Priestella, they regained their friendship after Subaru accidentally saved her by taking in the part of the Dragon Vein that Capella used to poison her.

Anastasia Hoshin
Subaru and Anastasia's relationship is somewhat complicated. In one loop where Subaru accidentally told information about Crusch's Camp she abandoned him after revealing that she was actually using him. Despite this, Subaru still saw her as a key potential ally alongside Crusch during the campaign to subjugate the Hakugei. Currently, their relationship hasn't improved, because Anastasia is currently possessed by Echidna.

Otto Suwen
After Subaru saved Otto from financial ruin and offered him a job as the minister of interior affairs for the Emilia Camp, the two became steadfast friends. Though their relationship has involved Subaru light-heartedly teasing Otto, the two of them are still rather loyal to each other, with Otto always having his best interests for Subaru in mind. Furthermore, Otto is one of the people Subaru trusts the most, and usually always talks to him first, before making any important decisions.

Petelgeuse Romanée-Conti
Petelgeuse and Subaru first crossed paths back in the early stages of Arc 3, during Subaru's 2nd failed loop. The Sin Archbishop ordered his followers to dispose of the Earth Dragon carrying Rem and Subaru and bring the boy to him, while killing the blue-haired maid. Upon waking up, Subaru was subjected to an unsettling scene of self-harming and madness, perpetrated by Sloth and his followers–a scene that would forever engrave itself in Subaru's mind. Soon after, Rem–mortally wounded but still alive–breached into the Witch Cult's hideout, however, Petelgeuse easily disposed of her with his Authority. The brutal action seeded deep roots of hate into Subaru's mind, and in the following loops, Subaru's hate for Petelgeuse would only continue to grow and escalate, due to witnessing the madman's campaign of terror through Irlam Village and Roswaal's Mansion, until, Petelgeuse became the person Subaru despised the most in the world, and was prepared to do anything in order to kill him. In the Arc's climax, Subaru would gather a subjugation force and tackle Sloth. It would, however, take two tries to defeat his body, but even utilising Julius' strength wasn't enough to defeat the Evil Spirit. It was only after a wild chase through the forest on a Dragon Carriage, that Subaru was able to defeat Petelgeuse by lighting him on fire and crushing him under the wheels of the carriage. Immediately following Petelgeuse's death, Subaru received the Witch Factor of Sloth.

During Subaru and Julius' fight with Petelgeuse, after Sloth possessed his body, Subaru felt he could understand and somewhat sympathise with the madman, though it didn't last for very long. In Arc 5, it is stated that Subaru felt absolutely no shread of remorse and hated his very existence from the moment the two first crossed paths a bit over a year before the events of Arc 5.

Furthermore, during the Subjugation against Greed in the latter half of Arc 5, Subaru deliberately referred to his Authority of Sloth as an Unseen Hand rather than Invisible Providence to crusch Regulus' pseudo-heart located inside Emilia's chest, likely in order to subconsciously prove Regulus wrong for berating Sloth's Authority for being too sluggish and weak – the very same Authority he considered to be miniscule in danger to him, proved to be his undoing.

Echidna
Echidna was greatly interested in Subaru's Return by Death ability, as it allows him to collect all kinds of information that no other person could. She later invited him to her tea party in order to strike a conversation with him and later even offered Subaru her assistance in the form of a contract. However, Subaru rejected the offer after the other witches gave him hints that Echidna wasn't telling the full truth, noticing that she is actually using him to satisfy her endless greed. After the other Witches helped Subaru realize how Echidna's only goal was to use him as a lab rat, he decided to cut all ties with her. His opinion of her corresponds with his opinion of Roswaal.

Garfiel Tinsel
Subaru helped Garfiel to understand the truth about his mother and became good friends with him. Despite his fights in the past, Subaru was still willing to talk to him. Their relationship eventually blossomed to that of a loyal subordinate and his captain, their camaraderie tied by not only that but also deep friendship.

Regulus Corneas
Subaru confronted him during his and Emilia's wedding in Priestella, which led to a battle that Reinhard joined in on and concluded with Regulus' death. Regulus and Subaru started off on a rather respectful note, but soon after exchanging a couple of words, they both started to strongly resent each other; Subaru's dislike stemmed from Regulus' abduction of Emilia while Regulus finds fault in Subaru's talkativeness and him disregarding his opinions which, which for him, meant that Subaru was belittling his rights, therefore he must be punished appropriately. Subaru regarded Regulus as an irredeemably evil person who had to be killed.

Lye Batenkaitos
Even though Subaru didn't know Lye that well, he felt immense anger and hatred towards him for eating Rem's name and memories ad placing her in a coma. Lye saw Subaru as his saviour as his Return by Death would allow him to experience tastes and memories like no other.

Vincent Abellux
Vincent and Subaru first met at the starting point of Arc 7. Though wary of Subaru's intentions, Vincent soon realised he wasn't in danger, letting his guard down and even helping him; a notion very uncharacteristic of the former 77th Emperor of the Vollachia Empire. Vincent even went as far as gifting Subaru a dagger with a Vollachian symbol embedded in it. The dagger later came to serve Subaru rather well, as he used it to cut his way through dense flora in the Buddheim Jungle as well as unknowingly getting on Todd's good side as the Captain thought Subaru was a Vollachian noble. In his third and current loop. Subaru and Vincent managed to get themselves entangled with the Sudrak Tribe, being forced to partake in the Ritual of Blood. After successfully defeating the giant black snake Demon Beast, Vincent asked Subaru to assist him regain the Imperial throne again.

In the following chapters, Subaru and Vincent often expressed their disagreement for each other's way of thinking as their mentalities continued to heavily clash against each others'; Subaru's idealistic and hero-like mentality could not comprehend Vincent's ruthless and cold, yet calculative tactics, and the fact he's willing to throw away innocent lives to further his own goals. With time, however, the two started to see eye-to-eye. Vincent started relying on Subaru as some kind of strategist, though Subaru is somewhat indifferent to Vincent, as he doesn't wish to view himself as his ally or accomplice.