Asia Argento

Asia is extremely shy, innocent and fairly inexperienced in things like socializing. As a former nun, Asia is a devout Christian, despite being reincarnated as a Devil, Asia still believes in God and follows his teachings such as praying to him and reading the Bible, which would usually result in her getting severe headaches. Asia has a strong kindness, even when she was still a human, she harbored no hate towards Devils and treated everyone equally, regardless of what they were. Azazel noted that her unconditionally kindhearted nature forces her Sacred Gear to heal even enemies, as she is incapable of turning a blind eye to the suffering of others. Asia was also in deep shock when she learned from Kokabiel that the God of the Bible was killed during the Great War.

While initially having difficulty adjusting to her new life as a Devil, she has stated that she has found more important things than her faith in God, those things being her new friends, comrades as well as Issei's parents and Issei himself.

Asia is noted to be a very pure individual as people are drawn to her and that she is easily liked by others. Her charm and purity is such as that she was able to tame Rassei, a Sprite Dragon despite being a Devil as normally Sprite Dragons aren't tamable by Devils and are only tamable by those with pure hearts. Azazel noted that she had outstanding talent for taming dragons, as after receiving Ophis' blessing, she was able to form a contract with Fafnir, one of the Five Great Dragon Kings. After she managed to tame 4 mass-produced Evil Dragons, her name was spread in the world of Dragons due to the fact that only Evil Gods were able to tame Evil Dragons, as she became known as the Dragon Priestess (龍の巫女, Ryū no Miko) among Dragons.

Due to having to give away her panties each time she wants to summon Fafnir, she has become very embarrassed due to seeing Farnir eat her panties to the point of escaping from reality, lamenting that she has become associated with panties. However, after seeing Fafnir's resolve to protect her against Rizevim, she has become a bit less embarrassed by it and can put her shame aside during battle when Fafnir is fighting for her intensely.

Asia has a love of agricultural work as she often does gardening and planting. She has even stated that she would like to live with Issei in the country side of the Underworld and do cropping along with other kind of agricultural work.

Asia would become more "bold" in her relationship with Issei when she saw the other girls being more intimate with him and dislikes the idea of being left out. Due to Issei initially viewing her as more of a sister due to his desire to protect her, he didn't ogle her like he did other women, causing her to be sad and develop a bit of a inferiority complex when it comes to comparing her looks to the likes of Rias. However, she will get jealous and pinch his cheeks whenever he lusts over other girls. She is shown to desire to be treated as a woman by Issei and to have his erotic behavior directed at her, as she has even shown a desire bear his children, though she ultimately succeeds in this endeavor after the Sports Festival when she kisses him, as following that point, Issei began to view her more as a woman than a little sister. Asia thinks very highly of Issei and has stated a desire to stay with Issei forever, even being willing to become his servant. Despite being shy, she is shown to be protective of Issei as she will slap someone like Diodora when they insult Issei.

After becoming Issei's servant, she has begun to shown more courage and determination in battle, as demonstrated in the Rating Game against Team Rias Gremory, where Asia stayed behind to fight Crom Cruach alone to allow Xenovia and Irina to proceed ahead as well to preserve Issei stamina, with Crom Cruach admiring her courage and guts. During the fight, she even displayed the ability to use magic offensively, in contrast to her past passive self, as she continued to fight Crom Cruach even after Fafnir was defeated, stating that as the servant and future wife of the Red Dragon Emperor, she would keep fighting until the end, which deeply impressed Crom Cruach as he praised her courage and spirit, stating that it was his honor to fight her and Fafnir.