Zest

Zest (ゼスト, Zesuto) is a Demon who originally served her creator, the Demon Marquis Zolgear, as his aide. She was sent by the Current Demon Lord faction to act as a scout alongside Lars to survey the conditions of Tōjō Residence. After Zolgear's defeat, she temporarily served Maria's Mother, Sheera as she lost her original purpose and meekly compiled the demand to join the Moderate Faction. She ultimately serves Basara as she was tied to Basara Toujou in a Master and Servant Contract through Sheera's curse.

Appearance
Zest is a tall woman with short white hair, tanned skin and golden/greenish eyes. She was created by Zolgear according to his tastes of women, and thus has shapely and sturdy figure. She has a tail which resembles a rabbit, which may imply that she may be created from the corpse of such animal. Her rabbit ear like horns also implied her peculiar origin. When in her battle attire is a revealing middle of her chest and tight black dress, with black gold shoulder plate and white stocking, this was also her everyday attire until she came to serve Sheera, which replaced it with a modest looking maid attire.

In Volume V, Basara noted that after serving Sheera, Zest's bust size grew considerably.

Personality
Zest is known to be fiercely loyal to her master. Cold and calculating, she never go against her master's decisions. She, however, does not practice blind obedience and would advise her master should she feels that her master's decisions would result in undesirable consequences. This trait was exemplified as she advised Zolgear to refrain from raping Mio Naruse before her powers are completely extracted, as this will result to the loss of her powers which was essential if Zolgear were to overthrow the current Demon King, Leohart.

Cold as she is, nonetheless, it did not mean that she did not have the capacity of having and feeling emotions. This was first implied when she scouted the Toujou Residence during Basara's subjugation of Mio and Yuki Nonaka, wondering if Zolgear would love her as Basara would to her servants, or what if Basara were her master instead, although she asserted that she felt "no jealousy whatsoever". Her emotions became even clearer as she served Sheera, and later, Basara. It appeared that she has a complex and constantly wonders whether she is useful enough to her master.

She is also revealed to have a humble and meek personality when she is not fighting her master's enemies, and is the only one amongst those bounded by the Master-Servant contract with him to address Basara with the honorific "-sama".

History
Zest was created by Zolgear to be his aide and guard, and was apparently made for that purpose only as she was created in a way that she'd lose all her powers the moment she lost her virginity, in contrast to all other girls in Zolgear's collection. She stayed true to this purpose, and was extremely loyal to her creator.

She was one of the two demons sent by the Current Demon Lord Faction to scout upon Naruso Mio alongside Lars, until Zolgear's ultimate plan came into motion as she orchestrated the plan to kidnap Mio, unbeknownst to the other members of the Current Demon Lord Faction.

After Zolgear's defeat, she temporarily moved into the Tojo household, though she ended up leaving as she was demanded to change her affiliations and defect to the Moderate Faction, serving Sheera in the process. When she was set to leave the Tojo Residence, Basara told her that she "is welcome to return to the house anytime", this was one of the factor which made Zest to serve Basara through the contract just before the Siege of Wilbert Castle, confirming that her loyalty lies not to the moderate faction, but to Basara instead, alluding to her original stance which was loyal to Zolgear instead of Leohart and his faction.

Demon Lord Sister Arc
She first appeared as she intervened Lars' debate with the other demon, and later revealed to be one of the surveillance team to monitor the Tojo Household as Lars was defeated in the end of the arc, during which he made a deal with Basara. Lars commented and asserted as he informed Basara that Zest would be a problem in days to come.

Kidnapping of Mio Arc
As she observed the Toujou Household, she witnessed the subjugation of Mio and Yuki by Basara, which made her, for the first time, imply that she has the capacity to feel. She wonders if Zolgear could love her as Basara did to his servants or if Basara were her master instead, but later disregarded this idea as a fantasy.

She later orchestrated the kidnapping of Mio with the reluctant Maria under the orders of Zolgear, which recently was forced to join the Zolgear camp after her alleged "sister" was kidnapped by Zolgear. She controlled Mio's friend to pounce on Basara, thus making Mio to throw a fit of jealousy and escaped the scene, during which Mio flee to a tennis court and was captured by Zest and Maria by making her unconscious, and then moved her to Zolgear's secret manor.

As Mio was chained by Zolgear, which rendered her and her magic completely useless, she advised against an eager Zolgear who originally planned to rape Mio to incite the Master-Servant curse to a maximum level that would fry Mio's brain and thus would effectively make Mio as one of Zolgear's collection. She told Zolgear that it'd be better to extract her powers first before doing so, as Mio, like Zest, would lose the power protecting her the moment she lose her virginity. Zolgear, however, was immediately interrupted when the current Demon Lord, Leohart, summoned him to survey a complex of ruins believed to host the bodies of ancient heroes, and thus hurriedly left the mansion to Zest as he grudgingly compiled to Leohart's request.

As Zolgear was absent, under the request of Basara, Lars infiltrated the mansion with an unconscious Basara and confronted Zest. He mentioned his purpose was to drop off the defeated Basara, which was also an object of Zolgear's interest as he was able to control the sword Brunhyld. He asked her whether Zolgear was responsible for the kidnapping of Mio, which was deemed illegal as Zolgear did not let anyone from the Current Demon Lord faction to learn that fact. Zest denied this as Lars pressed her to allow her to search the mansion, during which Zest deemed Lars as a threat to her master and supposedly killed him.

Later, as Basara was struggling against a deluded Maria, Zest came into conflict with Yuki who managed her way in by herself. Yuki has already freed Mio from her chains, and the combination of Yuki and Mio proved too much for Zest, she was later tied and was originally supposed to act as a hostage for the Moderate Faction, during which she may be able to spill the Current Demon Lord's secret. She, however, resorted to silence as Mio and Yuki planned their next move.

Zolgear, however, came back early from his trip and found Zest in her incapable state. He was not pleased by the fact that Mio was freed from her chains, but said that there's an additional girl (Yuki) for his collection and he was fine with it. As he said so, he deemed Zest was incompetent and was set to kill her, only to have his spell interrupted by Basara who has just sorted things with Maria.

After Zolgear's defeated later by Mio's powers, she was in a state of shock, losing her original purpose as Zolgear's aide, she gave in to Basara's proposal to temporarily move into the Tojo Household along with Sheera (which was revealed to be Maria's mother instead of the alleged 'sister') until the Moderate Faction pick them up. She'd still address Basara with his full name as the members of the household is constantly vigilant against her. Lars, who supposed to be dead, was alive and well, and later finished the affairs with Zolgear who managed to escape the fight after being injured by Mio's powers, as Lars ultimately killed him, effectively ending the life of Zest's first master.

Later, she left the household with Sheera to Wilbert Castle. Before she left, Basara told her that she'd always be welcomed if she wanted to return to the house, in contrast of how the other girls think.

Siege of Wilbert Castle Arc
She was left out during the Hijirigasaka Incident, but came into a prominent role later when Mio and Maria was summoned by the Moderate Faction, as the Moderate Faction have yet came to terms with Maria's early betrayal and deemed to have endangered Mio in the process. Zest was seen again as she came to Basara's party's room to serve tea, she had undergone a few physical changes, as the first thing that came into Basara's mind was "her bosom is now considerably larger".

Some time later, Mio was revealed to be in a state of cold war with the current Moderate Faction leader, Ramsas, as he refused to tighten the security around Mio after the incident with Zolgear. Zest herself was wondering her own position in the Moderate Faction, knowing that she has no actual reason to join the faction.

During a stroll to town with Basara and his company, she constantly wonders whether her current place is the place where she could belong. She opted to stay outside when Basara decided to enter a cafe while continue wondering. Now alone, she was confronted by the Moderate Faction guards who deemed her not trustable and her presence was unpleasant for the faction. As she was surrounded by the guards, Basara once again saved her.

This cemented her stance that her loyalty lies with Basara instead of the Moderate Faction. Just before the Siege of Wilbert Castle, as Basara was bathing, Zest and Sheera intrude themselves to his bath. Sheera insisted that Zest was there to serve Basara, which Basara strongly refused and told Zest that she has no obligation to obey Sheera. Sheera kept her stance, pressing Basara with the fact that she was Zest's master, not Basara, and she has no reason to listen to Basara. If Basara wishes Zest to stop, Sheera proposed that Basara should become her master instead. Basara asked Zest if she was okay if he were her master, and to his surprise, Zest agreed. Basara and Zest were later bounded by Sheera's spell.

Basara thought that the contract ceremony went well, as unlike the other girls, Zest readily kissed his hand to perfectly sealed the contract. However, the Succubus curse were nonetheless activated. Basara wondered why as Sheera warned that her curse is far stronger than Maria's, and Zest would go insane if left alone, he was left with no choice but to subjugate Zest like he did to the others.

After subjugating Zest once, however, the succubus curse came back into effect. It was revealed that Zest constantly wondered if she was worthy enough to serve Basara, which indirectly treated by the contract as an act of treason. Thus Basara had no choice but to continuously subjugate her until Zest came to the conclusion that "servants getting pleasured by their master is useless and it should be the other way around", and before Basara came to, he realized that he was extremely tired. Sheera noted that he climaxed five times and commented that Zest "sure is talented for the job".

During the Siege of Wilbert Castle, she was seen to fight alongside her new master against Leohart's trusted friend Garde and the army of ancient heroes which was revived from the ruins which was inspected by Zolgear. She was proven to be an excellent support for Basara as he needed elevations to battle against the giant heroes. Later, however, she was forced to part with Basara as she had to stop a giant's advance, and left Basara to fight Garde alone. The moment she returned to Basara, Basara was knocked out by Garde and was allegedly dead. But before Zest put her rage into motion, Mio had once again defeated the enemies in the same rage when she thought Basara was dead. Garde was captured in the process albeit Lars freed him again later. Basara, albeit heavily injured, managed to survive the ordeal and the siege was pulled as Zest embraces her master.

Powers & Abilities
Bladed Claws: Her claws are extremely sharp, akin to swords. Combined with her speed, she was known as the most deadly subordinate of Zolgear. When she allegedly killed Lars as she was confronted by him, it took for her just one strike. Her claws were also sharp enough to cut through the giant ancient heroes during the Siege of Wilbert Castle.

Magic Practitioner: She is well-versed in Earth Magic, and can act as a supporter or an attacker. She is able to shoot earth bullets and control its projectiles, and elevate the surrounding land to provide higher elevation should it is needed.

Relationships
Basara

Basara was originally Zest's enemy, until she was saved from her own master after she was declared incompetent. She continued to act cold and call him by full-name basis, but later she affirmed that she wanted to serve Basara after he saved her for the second time. She is shown to be explicitly loyal to Basara after her contract completion and wishes to be useful for him. She also harbors romantic feelings for Basara.

Zolgear

Zolgear was Zest's creator and her original master, she was engineered in a way that Zolgear would never touch her. Zest longed for Zolgear once, until she was cast aside by him as he wasn't pleased that Zest once wondered how things would be if she'd have a different master (which was Basara). As Zolgear's aide, she was known to be strong, fierce and most loyal to Zolgear amongst the factions.

Sheera

Sheera was Zest's temporary master. Zest has some attachment towards Sheera, perhaps out of guilt as she was responsible for Sheera's capture which lead to Maria's betrayal. Sheera was the one who taught Zest the skills of a maid, which became her new occupation while she was under Sheera.