Seira's appearance is that of a high school teen. Seira has pale skin and silver hair, which people have concluded to be natural, as it looks too real to be dyed or to be a wig. She has scarlet eyes, a common trait among nobles. She has been noted for her beauty by many different people, including other nobles.
In the human world, she wears her school uniform with some additional 'elegant' embellishments, and always looks neat and tidy. While representing nobles, she always dons an elegant black attire with emblems symbolizing nobles.
Before being a clan leader, she wore a black and white, high-neck gown with golden embellishments.
Seira is quiet and straightforward, and speaks only when she deems necessary. She is a fast learner as after a few lessons, she became solely responsible for making the meals in Frankenstein's house, with the one exception of being ramen, a dish in which Frankenstein is the sole undertaker.
Seira does not shy away from responsibility, and has undertaken the role of Lukedonia's representative when interacting with both the Union and the KSA.
Yuna and Suyi have expressed their envy over Seira as the only female in Frankenstein's household comprising of nothing but good-looking men. However, Seira views all of the men in the house as either her junior (since she is 217 years old) or as a mentor, thus rendering them all ineligible for her to develop a crush on.
Seira is difficult to agitate. When insulted or looked down upon by her opponents (for her age or her sex), she is completely indifferent. She loses her composure on certain occasions, such as the encounter with Zarga Siriana, the murderer of her father, or what she mistakes as the current Lord's assault on Raizel. She is also a big fan of praise, blushing whenever Frankenstein or Rozaria compliments her.
Seira has many admirers in the series, both friends and foe alike. It seems that Shinwoo has lately been developing some feelings for her, the way around when she is seen occasionally in a few moments helping him pick up his bag for him or even wipe Shinwoo face in front of everyone when he got a mark on the face while eating, which she appears to return (despite the problem of age difference that she feels with the men in her current household). Rael Kertia is a persistent suitor of hers who wishes to marry her; however, many suspect that he only wishes to win her heart to also win the position of the Loyard Clan Leader. Seira repeatedly says that Rael is "not her type" and his violent actions were also "not her type". It has been shown in several instances that his feelings for her are genuine. A recent addition to her admirers is Yuri, a spy of Dr. Crombel. Upon their first meeting she instantly captures his attention when he sees her poise, power, and beauty.
Seira J. Loyard is the last remaining royal member of the Loyard Clan, making her the Clan Leader. Her position is validated by her possession of the Loyard Family Soul Weapon--the Death Scythe.
She became the Loyard Clan Leader about 100 years ago when all of her family clan members were killed by treacherous clan leaders. This included her father who was killed by Zarga Siriana. Seira was the only surviving member of her clan after the incident which resulted in her becoming a Clan Leader even before her coming-of-age ceremony.
Since the death of her family members, she has been under the care of Gejutel who has a high esteem in her sense of judgement. Ten years before coming to the human world, Rael proposed to Seira. She rejected the proposal then. She is older than Regis and Gejutel trusts her to take care of him. She is seen as a frequent companion of his in the human world.
Seira and Regis are sent in the human world by the Lord of nobles to investigate the hospital massacre. There they pick Ye Ran to get admitted as students and reside in Frankenstein's house. Seira is taught household work by Frankenstein and she takes good care executing them. At nights, she and Regis investigate without knowing that they are watched over by Rai, Frankenstein and M-21. Both she and Regis develop suspicions regarding M-21 which clear up later on.
When DA-5 kidnaps Regis along with the children, Seira was at home. The sudden disconnection of her mind link with Regis compels her to think that he is in trouble so she sets off to search for him but not before using mind control on Rai and Frankenstein (assuming them to be humans) to stay put in the house (obviously it didn't work).
She faces Hammer on the way and brings out her Death Scythe to get rid of him. Later Frankenstein catches up with her and both are surprised to find something new about each other. Seira realizes that he is not an ordinary human while he reckons that she is the clan leader of the Loyard clan. However, the massive power flow caused by Rai who has been busy annihilating DA-5 draws their attention and they reach his location to find the situation all under control.
Later, Seira sends a report on their investigation mentioning the presence of likely nobles which later brings about the visit of Gejutel.
Gejutel pays a visit to Ye Ran and Seira and Regis take him to the place they have been staying at. There he meets Rai and Frankenstein. Before he leaves, he asks Seira of her opinion on the two (Rai and Frankenstein) and she replies that she trusts them. Gejutel agrees with her statement and re-affirms that they are trustworthy.
A few days after Gejutel's departure, a new visitor drops by and draws every nobles' attention by starting a conflict with the special security trio. Rael has come to take back Seira to Lukedonia. He proposes to Seira once again after his blunder 10 years ago, but she still rejects him like she did before. However, after Rael reveals that Seira has been summoned back to Lukedonia by the Lord, she quietly and promptly obeys the order and returns with him, leaving Regis with Frankenstein.
Upon her return, Seira is locked up in the room of discipline for her misinformation but she later manages to break out in order to try to stop Gejutel's death sentence. However, she is stopped midway through her escape attempt by Rozaria. The fight between the two concludes with Seira being overpowered and brought before the Lord to be punished alongside Gejutel.
Raizel's interruption and the revealation of his identity as the Noblesse, stops the execution of the punishment of both Gejutel and Seira in time. After all the misunderstandings amongst the nobles of Lukedonia are cleared up, Seira returns to the human world along with Rai and Frankenstein.
Seira is settled to doing chores and cooking meals for the entire household and the frequently visiting children. She also joins in rare unusual outings like- visiting Suyi's shootout. When KSA agents get involved with Ye Ran to check the skills of recruit candidates (Shinwoo and Ikhan), Seira and Regis are advised by Frankenstein to stay away from any sort of action that might give away their identities as nobles.
Cerberus members attack the KSA building and the RK team rushes to their aid. Regis and M-21 get badly wounded by Taze who arrives with the 12th Elder. Taze sends a final blow towards Regis with her weapon (which she boasts of as the Death Scythe) but the smoke dissipates to reveal Seira who arrives just on time to save him. Seira takes out the real Death Scythe. Although Taze mocks its appearance declaring that hers is far better, Seira simply shows no interest. This infuriates Taze who attempts to overpower Seira with a stroke of her scythe but Seira brandishes a counter-strike with the true Death Scythe which is powerful enough to shatter her scythe in pieces. She defeats Taze.
When they return home after Cerberus is annihilated and Rai has wiped out the existence of the 12th Elder, Rai tells everyone of the household to leave as they can no longer have peaceful lives they opted there. However, hearing from Frankenstein about Rai's worry, they decide not to leave. Seira becomes the fifth member of RK-5 team and they swear allegiance to Rai.
More elders begin to arrive and Seira goes along with Regis to meet the 10th and 11th Elders as the nobles formally representing Lukedonia. They leave with an unsettled issue.
When Tao and Takeo get kidnapped, M-21 and Rai go to look for them. Seira returns home with Frankenstein and Regis and finding them gone, they also depart to look for them. There Seira faces Rostere and gradually gains the upperhand. But before she could finish him off, Rostere thinks of using humans as live shield to getaway. Rai interferes in her fight then and defeats Rostere.
Having exerted lot of his life force, Rai enters a short hibernation. In order to become stronger, the RK team trains with Frankenstein in his island. Seira is left to watch over the house when the guys are training. She joins later and returns shortly after attending some training sessions with Frankenstein.
A sudden intrusion of three more elders in the city catches Seira's attention as the 5th Elder starts with a demonstration of destruction to call out any noble present there. Seira arrives to find a traitor clan leader, Zarga Siriana, present amongst the elders. He reveals that he had killed her father, the previous Loyard Clan Leader in the incident back a hundred years. Seira loses her calm and battles Zarga (answering the interruptions from the 8th Elder as well) but gains control once she recalls Frankenstein's teachings. However, that does not prove sufficient when Zarga brings out his soul weapon. The battle further tolls against Seira as the 8th continues to interfere with sudden attacks on her. She is overpowered and defeated but saved by Frankenstein just on time.
Later Frankenstein and Rajak join the battle against the Elders but even their combined force proves to be lacking against the 5th, 6th and 7th Elders (the 8th being defeated by Frankenstein). Rai arrives to save the three of them and takes care of the traitor nobles.
Seira and Regis visit KSA to inform them that Lukedonia would provide them with all possible help. Their meeting is cut short by the arrival of Ignes Kravei.
Seira battles with Ignes and her robo guards. She is ultimately defeated along with Rael who came to help her. Ignes takes Seira on Roctis' island to use her as an experiment specimen. Rael and Regis secretly track Seira and leave behind clues for Rai and team.
Seira, Regis and Rael are rescued by Rai, Frankenstein and Rajak. Seira and Regis feel guilty as Rai lost more of his life force because of them.
Seira makes very few appearances in Season 7.
At the end of Season 7, Seira comforts Rael who lost his elder brother, Rajak. She provides him moral support and a shoulder to cry on. She assures him that it's natural to feel grief for his deceased brother, as he was his family.
Seira is walking along with Yuna, Suyi, Rai and Regis, with Yuna and Suyi wondering about where Shinwoo and Ik-Han have disappeared to.
After M-21 finishes his battle with Aris, Mark and Yuri, due to Muzaka arriving, Aris decides she wants to take Shinwoo back with her as an experimental specimen. No sooner than she makes the request, Seira's Death Scythe is at her throat as a warning. Muzaka denies her request and they leave.
The children are at Frankenstein's home. Seira prepares a meal for them and Regis helps her to serve the food.
Seira and Regis are on standby at the school. Regis is frustrated that he and Seira can't help rescue M-21, since they have to guard the children and the school in case other enemies try to take advantage of the current crisis and attack. Seira assures him that their role is important as Rai and Frankenstein can now fight without restraint knowing that the children are safe. What annoys Regis the most is that M-21 is being used as an experiment specimen again, which for M-21 is a fate worse than death.
Gejutel K. Landegre: Seira has great respect for Gejutel, who has been her guardian ever since her entire clan has been wiped out by the plot of traitors. She even breaks out of the prison of the Castle, in disobedience to the Lord's authority, in order to stop Gejutel's execution.
Regis K. Landegre: Seira almost always accompanies Regis everywhere since Gejutel has appointed her with the duty to take care of his grandson. However, she refers to it as 'babysitting'.
Rael Kertia: Seira has clearly stated, time and again, that Rael is "not her type". At first, she treats his persistence as nothing but annoyance. However, the gradual change in Rael, as well as his help in many situations have evoked a relatively milder response from her.
Frankenstein: Frankenstein is a mentor figure to Seira. She cultivates her culinary expertise under his guidance as well as battle training. She is sometimes shown to blush whenever he compliments on her achievement.
Despite her young age, Seira is a Noble Clan Leader and is even stronger and more agile in her normal state in comparison to Regis. When she fights as a clan leader using her soul weapon, she can be deadlier than adults with twice her experience, like Rael. She becomes stronger as the series goes on as she has shown to be able to fight Union Elders and werewolves. When she fights Rozaria, she comments Seira has gotten stronger since the last she saw her. She defeats the captain of Cerberus with one strike. When the 11th Elder felt her power he wanted to fight her. She pushed agents and the 10th Elder during their battle & even made Zarga get serious during their battle.
Death Scythe: As the Clan leader (and the only remaining member) of the Loyard Clan, Seira utilizes the "Death Scythe," the symbol of the head of the clan and her Soul Weapon. Frankenstein noted after seeing her wielding the weapon that the myths of Death or the Grim Reaper carrying a scythe stems from this. She has been shown to be proficient in using it. She generally uses her weapon to slash the air to create an energy blade.
Grim Reaper: While using her soul weapon, Seira draws a black circle by using her energy. The circle releases massive amounts of spiritual energy. Seira can perform a powerful attack that turns the radiated mass of energy into a mirage of the Grim Reaper which draws skyscrapers. The slash of Grim Reaper is more powerful than other slashes and has dealt huge damage to an Elder easily. As an energy-based form, it can be destroyed by energy-based attacks. Unlike other animal-based ultimate attacks, this technique uses spiritual character.
As a Noble, she possesses great amounts of strength, speed and regeneration. She is shown to easily defeat even modified humans such as Hammer from DA-5 by just using her hands and great speed. She usually fights using her hands to slice her opponents instead using her fists. Seira is shown to have great speed as she can even keep up with the likes of Rael, who is (with the exception of his brother and Clan Leader, Rajak) the strongest among the Kertia clan. She tore a hole in a metal cooking pan simply by flicking it.
Superhuman Strength: Seira possesses vast amounts of strength, being able to destroy the surrounding area and create large craters with casual punches.
Superhuman Speed: Seira is fast enough to keep up with extremely fast opponents such as Rael, who easily moves in hypersonic speed.
As a Noble Clan Leader, Seira possesses immense amounts of spiritual energy (aura). She can produce force fields to protect herself and her allies as she did when Frankenstein and Rael were fighting.
Mind Link: A psychic link established between Regis and Seira. It works up to a certain distance, so they can communicate if necessary. Thus, she is constantly able to sense his presence, unless he is out of the range, unconscious, or dead. This skill was shown to be useful when Regis and the children were taken hostage by DA-5.
Clairvoyance: In the battle between Frankenstein and Rael, Seira expands her senses to search the area for humans to prevent causalities
Besides her fighting skills, she is very skilled at cooking. She easily learns a recipe and prepares it perfectly. After staying in Frankenstein's House, she has learned many recipes and has trained her cooking skills. Currently, she possesses vast knowledge and the capability of preparing almost any kind of food with a strong sense to the aesthetics of cooking. However, she generally prepares ramen for Rai's obsession with it.