Although many people ignore him or are annoyed by him because of his immaturity, loudness, and pridefulness, Black☆Star's friends see him as reliable, talented, strong, and passionate. He frequently picks fights with other students, even older students, but he rarely loses. Teachers are annoyed by his class clown antics, even as they admit he is full of potential. Throughout Soul Eater, Black☆Star slowly gains the respect of both his DWMA allies and his opponents--even if he is still seen as immature.
"Black☆Star's an idiot by nature. But I like him that way. That's just our team's style."
Tsubaki's attitude is more reserved and quiet which makes her the complete opposite of Black☆Star. However, despite their different personalities, they are rather close, sharing a strong relationship.
Black☆Star still brags to her about his abilities like he does with everyone else, and becomes impatient with her when she does not agree with him, up until the point he abandons her to fight on his own at one point. But despite these occasional setbacks, Black☆Star still genuinely cares for Tsubaki, and is very protective of her. As she is the only one who had not ignored Black☆Star and the only one who had accepted him as he is, she means a lot to him. When others would mock him for seeming to lack talent or practice, Tsubaki is one of the first persons to defend him. Even if her defense acknowledges his flaws, she has confidence he can improve. Therefore, Black☆Star knows that she is a person that can be relied on, and also does not like to worry her.
Although Black☆Star is not normally good at reading other people's emotions, he catches on easily to Tsubaki's, and always tries to cheer her up when she is upset, most notably when he offers her a hug after she defeats her brother. His arrogance is toned down a little when he is with her, and he acts more relaxed, showing that he can be more like himself around her. Tsubaki is also one of the few people that Black☆Star actually listens to, and he occasionally even follows her advice at times.
While he does not express it directly, he appreciates Tsubaki fighting alongside him and helping him. The two work well together in battle. It is implied that he takes pride in having her as his weapon. He occasionally depends on her to sort out anything that he cannot, such as fights between him and his friends. Consequently, he is prepared to shoulder a great amount of responsibility in order to help her in any way. He decides to follow the 'Path of the Warrior' in order to fulfill Tsubaki's brother's unfulfilled dream, which results in Tsubaki being reduced to tears.
Like any practiced meister-weapon pair, are always concerned about the other's safety. When Black☆Star is injured in battle, Tsubaki frequently calls out his name, and will express grief in tears or her words.
Black☆Star also appreciates her support, and sees her as a light in the darkness of his heritage as a member of the Star Clan, and he comments that if he is the dark night sky, then she is the shining stars.
At times, Tsubaki expresses annoyance with Black☆Star, such as when he desires attention even on covert missions. At her worst, she is willing to call him an "idiot." However, at the same time, even in some of their earliest missions, Tsubaki showed far more deference to her meister, referring to him as "sir." At one point, he calls her by the affectionate term, 'Tsubaki-chan'. 
Black☆Star's father. He does not know White☆Star personally, he bears no grudges against this as he knows that his father had been a criminal, and he had paid the price. However, White☆Star and the Star Clan's history is shown to be a source of insecurity for Black☆Star, and because of his father's actions, he is often ostracized by people victimized by the Star Clan. At one point, Black☆Star unintentionally begins to follow in his father's footsteps, becoming hungry for power and on the brink of following the 'Path of the Demon.' However, he soon realizes that this is wrong, and starts following the 'Path of the Warrior,' and he finally comes to terms with his heritage as the Star Clan, leaving White☆Star's influence behind him.
Not much is revealed about Black☆Star's mother. His opinion of her is the same as his father, that by being killed by the DWMA, she had paid for her crimes.
Their personalities are rather similar, both being very headstrong and stubborn, thus, they get along very well and enjoy each other's company, with the two exchanging a high-five almost every time they meet. The two once even try to fight as Weapon and Meister, but end up failing miserably. Despite this, they still decide to be friends. Black☆Star understands Soul quite well, and of his desire to protect Maka, and he acts more serious when such a subject arises. He also trusts him in keeping secrets from others. As both of them mature, their friendship does so as well, and Black☆Star soon begins to respect Soul's cool-headedness and sound judgment. However, they also begin to slightly conflict, since their personalities are now more different, as Black☆Star does not agree with Soul in terms of keeping Mifune's death a secret to Angela. Black☆Star also admits that Soul, along with Maka, can be capable of things that even he cannot do.
Despite having completely opposite personalities, Maka and Black☆Star are good friends. They apparently know each other from childhood, since they had grown up together in Death City. Black☆Star likes annoying Maka and has fun winding her up because of how serious and mature she is in stark contrast to his immature and joking personality. However, he still cares for her deeply. He always will help her in battle when she's in trouble, although he often brags about it to her afterwards. He still respects Maka's wishes, and leaves her to fight alone if she wants to. Black☆Star still sees her as a friend, shown when he swears vengeance on Arachnophobia for hurting her and fights Mifune to get revenge. He also shows fury at Crona for betraying her. He understands Maka well, and has faith in her, although he does not often show this.
Although they are close friends, they do have their share of fights and arguments, since their personalities are completely different. There is an especially tense moment between them when they are training to achieve a Chain Resonance. Black☆Star begins insulting Maka, calling her an idiot and weak, and blaming their inability to achieve a Chain Resonance on her. Maka loses her temper with him and the two end up getting into an argument, which ends with Maka punching Black☆Star and running off, in tears. Black☆Star recognizes he was being a jerk, however, and says he deserves Tsubaki's punch after Tsubaki punches him when Maka leaves. Tsubaki goes to talk to Maka, and reminds her that despite their different personalities and that she might get annoyed with Black☆Star, deep down they have always been good friends. After being reminded of this, Maka decides to accept Black☆Star the way he is despite their differences, which thus allows them to finally create Chain Resonance successfully.
After, when they successfully achieve Chain Resonance, Maka asks Black☆Star to punch her since she had punched him back when they had been arguing. Black☆Star grins and says that he would not hold back. In the end, Black☆Star's punch sends her several feet backwards and into a dumpster. Despite being in pain, with a large bruise on her face, she smiles and the two make up.
Black☆Star also respects Maka for her abilities, saying that she and Soul are capable of things that even he cannot do. He also envies her ability of Soul Perception. During the fight with Crona on the moon, he deflects numerous attacks for her and defends her from the kishin's attacks as well, most notably when he kicked Asura after the kishin had stabbed Maka's shoulder with Vajra, gravely injuring his left arm in the process.
Maka and Black☆Star seem to spend a lot of time bonding and enjoy each other's company, for the most part. In the anime, Maka goes to see Black☆Star in the hospital after Kid hurts him in their fight to ensure he is all right, and Black☆Star always does the same for Maka whenever she gets hurt. They also go on a lot of missions together whereas Kid often goes on missions on his own, and Black☆Star is usually respectful of Maka's decisions as the leader of their team. Overall, they have somewhat of an older sister and younger brother relationship - they can get frustrated with each other easily because of Maka's maturity compared to Black☆Star's immaturity, but they also care deeply for one another's safety and will always support each other.
Black☆Star, at first, does not like Kid that much. Since Black☆Star's aim is to surpass the gods, Kid is a rival to him as he is a Shinigami, a God of Death. He often challenges Kid and picks fights with him in order to beat him. Their two conflicting personalities also causes them to argue at times. However, mostly, they still get along reasonably well, and make a good team in battle. Despite this, his jealousy of Kid's god-like abilities soon consumes him, which causes Black☆Star to goad him into fighting him, with Kid winning quite easily because of the unstable state of mind of Black☆Star. After that battle, Black☆Star then starts to respect Kid a lot more as he begins to understand what he wants to do.
He also respects him as Kid was the only one who took Black☆Star seriously and did not look down on him when he claimed to everyone that he will surpass the gods. He is grateful to Kid for helping him open his eyes to everything, and in return, he saves Kid from the insanity inside the Book of Eibon and vows to become stronger in order to help him maintain peace and balance in the world. Kid even stated that right now Black☆Star is the strongest in Shibusen and that he'll surpass him again. Black☆Star is now good friends with Kid, with all signs of rivalry and hostility gone between them. Although their personalities are still rather different, they get along quite well, sometimes even engaging in friendly banter.
Patty and Black☆Star seem to be good friends, both loving to joke around and play pranks on people. They often joke around together along with Kilik Rung and once, the two team up to ruin Liz's attempts to get a date, with the two bursting out laughing at the end. As Patty's skills in hand-to-hand combat becomes apparent to everyone, however, Black☆Star seems to treat himself as her senior, implying that Patty does not know how tough the world can really be. However, he respects her skills and her dedication as Kid's partner.
Kilik is Black☆Star's friend and occasional rival when it comes to sporting events at the DWMA. Both of them being rather laid back, cheerful and headstrong, they get along well, often joking around together. Although they squabble from time to time, in the end they are quite good friends and are willing to help each other out when the other needs help. Black☆Star is also not afraid to accept help from Kilik, although he does so with slight reluctance due to his pride. It also should be noted that Kilik is the only person who refers to Black☆Star by anything other than his full name, giving him the nickname "Swa-Star" or "B☆Star".
Black☆Star at first, thinks Hero as nothing more than a living training dummy for his fighting skills, not really caring whether he gets injured or not. When Hero acquires Excalibur however, Black☆Star is angered by the Meister's arrogance and attempts to put him in his place, although he is subsequently beaten by him. However, after Hero returns Excalibur, the two seem to have improved their relationship, as Black☆Star is seen actually talking to him rather than using him as a training dummy.
Black☆Star sees Stein as a rival, since he is the strongest Meister to graduate from Shibusen. He, one time, snuck into Stein's house to get answers to a test and got beaten up. But still he is in a positive mood after that. He leaps at the chance to fight him, and does not show him that much respect, often calling him names and being rather foul-mouthed and bad-tempered around him. Deep down however, he still follows and respects Stein as a teacher and superior. When Black☆Star matures more, he starts to show Stein more respect, and starts to call him 'Professor' for the first time. He looks up to Stein more as a teacher and even admits how he surpasses him in terms of Soul Menace capabilities. They become sparring partners after the defeat of Arachne as they are both rather equal in terms of combat skills.
Sid is the person who adopts and raises Black☆Star after the Star Clan is wiped out. Although Black☆Star is still bad-tempered and defiant around him, especially when Sid first becomes a zombie, it is shown, mainly through flashbacks, that the two do share a strong father-son or student-mentor relationship. Black☆Star also treats Sid as his equal, not as someone below him.
Although most students respect Shinigami, Black☆Star is the exception. His joking behavior and sense of humor is still present, even when around him, which often earns him a chop to the head from the Shinigami. He even offers him his autograph, which implies that he views Death as less than him, intitially. He also refers to Shinigami informally as 'Boss' (旦那 Danna in Japanese). However, like Kid, he has also shown during the main group's fight with Asura that he does harbor immense respect for him and has no problem fighting for DWMA's cause.
Mifune plays a prominent role in Black☆Star's life, being one of the people who help him grow past his arrogant thirst of power. Black☆Star is hostile to Mifune at the start of the series, as he has defeated him in battle and angers him by calling him a 'kid' and 'small fry', something that he hates to be called. However, a part of him does respect him for his strength and righteousness, and the fact that his wisdom had helped him grow stronger.
At the third and final fight to the death between him and Mifune, Black☆Star is no longer dismissive and hostile towards him, and instead calmly accepts and respects him as a fellow opponent who he will overcome in order to master the way of the warrior. The fight ends with Black☆Star ultimately killing Mifune. He swears to him that he will become a Warrior God, and this, along with his desire to assist Kid, fuels his drive to become stronger. Even after death, Mifune bears a strong presence over Black☆Star, up until the point that he adopts some of his Infinite One-Sword Style in his attacks, as if in homage to him. Black☆Star acknowledges that Mifune was a good man at heart, and has a strong feeling of regret for his death. Black☆Star is also openly sad about Mifune's end, being angered when Kid states that people do not need to feel feelings towards overcome opponents.
Black☆Star immediately befriends Tsubaki's father when he visits the home of the Nakatsukasa Clan in Japan, and they share almost a father-son relationship. Black☆Star acts more like himself around Sanjuro like he does with Tsubaki, and is not afraid to tell him of his raw determination to grow stronger, even if that means walking the 'Path of the Demon.'
At first, Black☆Star dislikes the Will of Nakatsukasa as he does not let him use his power, calling him 'Stupid Deer' once, but at the same time he is startled at his statement that he is like a demon. There may be a part of him that is slightly afraid of the Will. Although rebellious of him at first, he soon realizes the truth in the Will's teachings and decides to follow the Path of the Warrior, leading to the Will finally accepting him and the two begin to work side by side. Black☆Star probably now has more respect for the entity dwelling in the Uncanny Sword.
Angela was supposed to be Black☆Star's intended target in order to acquire a Witch Soul. However, after finding that Angela is a defenseless child, he lets her live. Although Black☆Star is slightly annoyed by Angela's tendency to be a bit violent at times, the two share a brother-sister like relationship when Angela is accepted into the DWMA.
When Crona joins Shibusen, Black☆Star immediately treats them like a good friend, promising to come to their aid if anyone is bullying them. However, even he admits that Crona is almost always depressing. When Crona betrays Shibusen, Black☆Star grows furious with them, as they had betrayed Maka, but still sees them as a friend, as he tries to get Crona to trust him. Black☆Star also shows a form of sympathy towards Crona as he comes to the realization that Crona has begun to lose their mind, and forgotten everything that has happened at the DWMA.
Black☆Star, uniquely, is the first person to directly ask Crona what gender they are in his own inappropriate way. Supposedly, Black☆Star assumes that Crona is a boy.
Black☆Star is at first, excited at the prospects of wielding Excalibur, after hearing that the people who had wielded him had become heroes, even kings. However, he is quickly disgusted by Excalibur's intolerantly arrogant behavior and annoying mannerisms. He is often disgusted even at the mention of him, and is notably the person most annoyed whenever he meets Excalibur.