She is proud of her family's name, but she does not like being seen as Rias of the Gremory Family. The reason for her living in the human world (as revealed in Volume 2 of the novels) is because there, everyone sees her as Rias, not as a Devil or as the Crimson-Haired Ruin Princess. Due to this and the fact that the only men who showed interest in her were interested in her due to being the Heiress of the House of Gremory, Rias soured on the idea of finding a lover, until meeting and falling in love with Issei. According to Akeno, Rias originally said that all men looked the same to her as Rias said that Issei is the only exception due to her thinking of him as cute. She thinks of Issei as a special person and always gets jealous when girls are around him, becoming a totally different person when she sees him and other girls together, or when it comes to training. Despite her mature stature like a woman, Rias tends to act her true age and becomes frustrated whenever girls flirt with Issei. While Rias is usually calm and mature in most situations, she loses her mature aura and presence when she sees any girl (especially Akeno) flirting with or seducing Issei. She enjoys teasing Issei and Asia (from Volume 3 of the novels onward), but at the same time makes it clear (to Asia or any girl) that Issei is hers, and she does not want to share him at all (It is revealed in Volume 3 of the novels that the Gremory Family and their servants are beings with extraordinary affection among the Devils, so Rias is no exception). She has no problem with showing Issei her breasts or sleeping naked with him (which she always does according to her and she claims she can't sleep without being nude or without Issei). Despite being seductive like Akeno, both of the girls are still innocent to love, as both of them become their age whenever around Issei or on a date with him. After becoming Issei's girlfriend, Rias begins to show more confidence in her relationship with Issei and is no longer jealous or angry when Issei is with other girls like she previously was, even accepting Issei's dream of having a harem and letting the girls have dates with him. However, Rias still shows some signs of jealousy such as when Issei doesn't spend enough time with her, but still believes in him and loves him. Due to being Issei's official girlfriend and later fiancée, the other girls acknowledge her as the "Legal Wife" as she manages the other women who are in love with Issei. According to Ravel, the burden of Rias as the "Legal Wife" is greater than the burden of Issei as she has to manage the girls maidenly feelings toward Issei and balance out Issei's feelings toward each of his lovers/brides. Like Akeno, Rias shows a sign of dependence toward Issei (possibly lesser than the former) as Rias will lose her will to fight and lead. She developed an instinct when Issei is with an unknown woman or other girls tried to seduce him before her she immediately rush to him quickly. She holds her older brother, Sirzechs, in high regard (despite her older brother's antics of being a siscon) because she deeply cares for him. When she was a child, she was entirely dependent on him and held him in admiration, while also feeling inferior to him at the same time. Rias loves participating in Rating Games, as she dreams of becoming the Rating Game champion by defeating the current Rating Game champion; Diehauser Belial, with the help of her peerage. While Rias is a powerful devil in her own right, being much stronger than average High-class Devils and according to Azazel, being able to become a Ultimate-class Devil just on the virtue on her talent alone, Rias suffers a bit of an inferiority complex when she compares herself to her fellow Rookies Four colleagues, as she feels inferior to Sona as a strategist and that she is far weaker in power than Sairaorg. However, according to Riser and Azazel, Rias has a talent for finding and recruiting talented individuals for her peerage, inspiring great loyalty and growing stronger with them as seen in her meeting with Issei. Rias is competitive and hates to lose, especially after losing her first Rating Game against Riser as she strives to always win, whether it is in sports or Rating Games. Due to being spoiled by her father Zeoticus and her brother Sirzechs from an early age, she has a somewhat impatient and selfish personality and because of her bad money spending habit, her mother Venelana and her sister-in-law Grayfia often scold her for her frivolous spending, as her mother reconsidered the amount of money she is allowed as allowance. Early in her childhood, she developed an instinctive fear and hatred of camels due to being hit by a camel after making fun of it, as the fear is great enough that the residents of the Gremory territory constantly keep camels away from her despite the Gremory's association with camels in the Ars Goetia. Due to being taught about Japan from Souji Okita, Rias has developed an obsession with Japan, buying various Japanese souvenirs and being ecstatic while visiting Kyoto during her school field trip, though she became pouty and stomped at the train station due to being unable to fully explore Kyoto. Powers & Abilities Equipment (Source: High School DxD Wiki)

Zack has a mental disability, whether it was something he had since he was born or he developed at some point in life is uncertain. This disability consists of him having a lust to destroying things, even to the means of killing. His blood rushes to a certain point and causes him to lose control of his urges. He will go into a short phase of destroying anything in his way until he's satisfied or until he rehabilitates. However, it can be regarded that while Zack is not academically intelligent, he is high in instinctive/survival intelligence, where he relies on his instincts to get him through situations, and can be seen as clever. Which could be how he was able to survive as a child, and up until now. And perhaps can even be described as an animal in a way. Zack is also extremely strong and rather fast, being able to run at rather incredible speed rates, and overall is actually a rather powerful character, which balances out the fact he isn't that smart. Zack is also VERY brutally honest, as he hates people who lie with a burning passion, and never ever sugarcoats anything he says. As a child, Zack was seemingly much more quiet and reserved. He was shown to never say a word throughout the manga specifically. Zack's first murder: He stayed in a run-down orphanage where children were likely to die, and the trafficking was illegal. His caretakers were rather abusive, and always referred to him as a monster, and even forced him to bury the corpse of a dead child simply because they didn't want to deal with the smell. Until one day, one of the caretakers left the TV on, where it showed a horror film that included a serial killer. And Zack just-so-happened to stumble upon it while it was on, becoming fascinated with the murderer specifically in the film. And he took inspiration from it, and he murdered his caretakers by mutilating their bodies, and later buried them in the back. And years later, his recent killings became famous, and is currently a wanted criminal. (Source: Satsuriku no Tenshi Wiki)