Akeno is madly in love with Issei but she cannot be his official girlfriend because he loves Rias. Akeno cares a great deal for Rias and does not want to destroy her relationship with Issei, even claiming that she will be Issei's mistress. She becomes a rival for his affections in Volume 3 and later falls in love with him completely in Volume 4 of the light novels. Her feelings for him continue to grow stronger as the series progresses, especially in Volume 7 after Issei relays her true feelings to her father. She loves Issei as much as Rias and needs him as much as she does, which was shown after Issei died in Volume 11, becoming devastated and severely depressed as much as Rias was, and thus becoming thrilled when she found out that he was alive. In the short story "Let's go to Onsen", when it appeared that Grayfia was attempting to seduce Issei, instead of becoming mad with jealously, Akeno instead reverted to the catatonic depressed state.
Akeno is Rias' first peerage member and one of her closest friends. Akeno is, in fact, close enough to call Rias by her first name in private while maintaining their master-servant relationship. After moving into the Hyoudou Residence, Akeno starts to call Rias by her first name when in the house and the two constantly get into a bicker (such as pillow fights) to see who gets to accompany Issei. Despite so, the two of them care greatly for one another.
Akeno cares for Asia like her own little sister. Asia also respects Akeno despite being love rivals for Issei's affection.
Koneko is Akeno's love rival for Issei. Despite this the two are on generally good terms with each other.
The two get along quite well with each other.
Akeno, initially didn't get along well with Azazel who is a Fallen Angel like her father. Azazel, on the other hand, cares a lot for Akeno since she is the daughter of his good friend Baraqiel and treats Akeno like his own daughter. After Akeno reconciles with her father, Akeno and Azazel's relationship also improves over time. In Volume 12, Azazel gave Akeno bracelets that brings out her fallen angel potential, which she used to overpower the Khaos Brigade.
Baraqiel is Akeno's father. As a young child, it is suggested that the two were close, but that changed with the death of her mother, Shuri Himejima. Akeno blamed her father (later acknowledging that it was better to have someone to blame to preserve her own sanity) creating an estrangement between the two that lasted for several years. It wasn't until the pair met again in Volume 7, and with the support of Issei, Akeno and her father were reunited. Baraqiel later trained Akeno in using her Holy Lightning.
Akeno had inherited her sadistic side from her mother, Shuri Himejima, whom supposedly had performed SM acts every night with her husband, Akeno's father, Baraqiel. It is implied that she also has a masochistic side that she inherited from Baraqiel himself.
Akeno met Venelana shortly after she arrives at the Gremory Palace. According to Akeno, Venelana was the person who taught her the way a lady should act, different kinds of knowledge, and even studies.
Akeno has great respect towards Sirzechs as one of the leaders of the Devils as well as Rias' older brother. Sirzechs is shown to treat Akeno like his own sister, taking care of her well-being.
Akeno has been shown to have great respect for Grayfia, and is also a fan of the love story of Grayfia and Sirzechs.
Akeno is shown to be close enough with Millicas to call him "Millicas-kun". Millicas also treats Akeno like his own sister calling her "Akeno-neesama".
Akeno was very close with her mother and loved her mother dearly, as such the events of her death left a scar in her heart, resulting in her hatred towards her father. Akeno has inherited her sadistic side from Shuri as her mother had performed SM acts with her father, Baraqiel, every night.
Akeno and Sona are shown to be good friends in real life, calling each other by their first name when in private. and when they go shopping together.