Hestia has feelings for Bell but he doesn't return them due to the thought of respecting Gods and Goddesses. She is also possessive and often tries to ward off other girls, especially Ais Wallenstein, from Bell.
As of volume 8, Bell has decided to accept Hestia's feelings instead of just respecting her, however it is unknown whether he feels anything for her in return.
Bell and Lili have a very friendly relationship. Bell has gone to great lengths to save Lili, the first time in the Dungeon and the second time from Finn after she supposedly accepted his proposal. Although he likes Lili, he is still oblivious to her feelings. However, he has started to think about her after Lili teased him as an older sister.
Bell first met Ais when she saved him from a minotaur. Because of that, Bell fell in love with her and gained the skill Liaris Freese. Ever since then Bell and Ais have had a friendly relationship with Ais assisting Bell whenever he needed help, such as before the battle with the minotaur and before the War Game with the Apollo Familia.
Bell and Ais have a positive relationship as she constantly helps him and she even accepted his invitation to dance even though it was her first time.
Tiona has a friendly relationship with Bell. She's been interested in him ever since he defeated the minotaur. Tiona calls him Argonaut-kun, and was even willing to help him train with Ais. She also excitedly told Gareth Landrock about how cool Bell was.
Bell met Syr on his way to the dungeon, when Syr called him over to give him a magic stone he had supposedly dropped. Ever since then she has made lunch for him almost every day and has worried for his safety in the dungeon. Bell acquired his magic when Syr loaned a Grimoire to him. After she witnesses Bell defeat a Silverback, she confessed to him that she fell in love with him after witnessing that feat though Bell assumed she was just teasing him.
Ryuu is on good terms with Bell, who she thinks will eventually wed Syr. Ryuu has been shown to have feelings for him, though she tries to keep them to herself out of respect for Syr.
Bell rescued Haruhime despite her thinking that as a prostitute she shouldn't be saved. He proved to her that a hero will save anyone regardless of the circumstances. The two have a very friendly relationship with Bell trying to help Haruhime whenever he can and Haruhime in turn tries to do her best. She is in love with Bell.
Bell became acquainted with Welf after using his former gear. Later Bell made a contract with him to form a party. Welf is grateful to Bell for wanting his work and not magic swords even after knowing his past. He acts like an older brother to Bell and takes care of him as best as he can. Welf even converted to Hestia Familia to help Bell.
Eina has been Bell's dungeon adviser since he registered to become an adventurer. Due to her past, she takes their relationship as adviser and adventurer seriously, warning him to not go on an adventurer and teaching him about the various dangers of the dungeon. She originally thought of him as a younger brother, but after the events of volume 11 she begins to develop personal feelings for him.
Due to her personality, Mikoto felt bad for pass parading Bell and his companions, and has supported him since then, first as a member of the Takemikazuchi Familia, and later as a member of the Hestia Familia after converting to assist him in the War Game.
Bell's adopted grandfather and his only family member growing up. Zeus nurtured Bell's desire to one day travel to Orario and be a hero, as well as his desire to have a chance encounter with a girl. Bell loved Zeus dearly, and he was filled with a deep sense of loneliness upon hearing of his grandfather's supposed death. Whenever Bell is unsure of himself or what to do, he thinks back to a piece of advice Zeus once told him or would imagine what he would say now if he were there, giving Bell the resolve and strength to move forward.
As of yet, Bell does not know that his grandfather is still alive, nor does he know that he is actually a God.
Wiene is the first Xenos that Bell befriended and the one he is closest to. Upon their first encounter, Bell was stunned upon her more human appearance and the fact she wasn't showing behavior typical of a monster. He tried to pretend he didn't see her at first, but rescued her when he saw that even other monsters attacked her. After discovering that she could speak and smile just like people, he decided to protect her.
Bell cares a great deal about Wiene, teaching her some things about the surface world and being gentle with her. In turn, Wiene trusts Bell above everyone else, even refusing to leave his side for a time. When Bell and the rest of the Hestia Familia were tasked with bringing Wiene to the Xenos hidden village, he was saddened that he had to leave her behind, promising her that they would see each other again.
When Lyd told him that Wiene had been captured by hunters, he became determined to help find her, despite the Lizardman's objections. When her Vouivre's Tear was ripped out and she went on a rampage on the surface, Bell protected her from other adventurers, though it caused his reputation to plummet. When Wiene's magic stone was cracked, she told Bell that she was happy he was there to save her and that she loved him before turning to ash. Bell was heartbroken and was about to cry out in grief if not for her resurrection by Fels.
Even with his reputation in shambles, Bell still wanted to help Wiene and the other Xenos that were trapped on the surface make their way back to the dungeon. Bell even fought against Ais to protect her, desperately trying to convince the Sword Princess that Wiene was not like other monsters. Before parting ways, Bell promised her that he would make a world where they could live together, using a pinkie promise at Haruhime's suggestion.
Asterius is the Xenos reincarnation of the Minotaur Bell defeated on the ninth floor. He was reborn through his extremely strong desire to have a rematch with Bell. After losing to Asterius in a close battle, Bell resolved to grow even stronger. He views Asterius as his rival and desires to be strong enough so that he can one day settle the score.
Bell's fight with Asterius also caused him to mature, as he became more calm and level-headed upon ascending to Level 4. He decided to study his magic and skills instead of just using them, trying to discover any new techniques that he could use against Asterius, like Argo Vesta.