Eshros is a humanoid child Mamodo with blonde hair. His true face is blue on the left and right sides, from the ears to the centers of his eyes, and with two lines at angles beneath his eyes in the blue sections, pointed teeth, and eyes with red sclera, small sky blue irises, and slitted pupils. He is, however, capable of disguising himself with an ordinary human face. Aside from that, he wears a light purple button-up collared shirt, brown shorts, white socks with light blue striped around the tops, and green tennis shoes.
Eshros' personality is selfish, arrogant, manipulative, impatient, and rotten to the core. He shows no concern for anything aside from his own ambition to grow stronger and become king, evidenced clearly by his impatience and lack of concern shown with Shin's kind and selfless actions. Despite this, he has enough patience to act as though he's doing it for mutually beneficial reasons. He manipulates his partner into performing wicked actions by twisting advice that the man received from his late mother, and only gloats over the wickedness in his actions and the effects that they have. He takes great pride in his power and abilities, but is nonetheless shown to be somewhat cowardly in the face of insurmountable foes, as seen when Shin stood up for himself.
Shin is a very tall and very muscular young man with short brown hair and gray eyes, as well as light lines underneath his eyes running to his chin. His outfit consists of a light green shirt with orange parts around the ends of the sleeves and collar, light blue jeans, a black belt, and blue and white tennis shoes.
Shin is a selfless, kind, gentle, and naïve young man. He often goes out of his way to help others, and has never acted out on his anger regardless of others' actions towards him. The only exception to this is when he understood Eshros' true personality, and yelled at him. Shin thinks very fondly of his late mother, and strives to please her in everything he does.
Eshros had nothing but contempt for his partner's gentleness and naïveté, but pretended to sympathize with him in order to utilize his power. Shin followed Eshros' advice with reluctance, working to help them both to grow stronger based on advice from his mother. Out of all the mamodo teams in the tournament, Eshros and Shin probably have the weakest bond. Even most evil mamodo have some connection to their partners. However Eshros works poorly with his bookkeeper due to his selfish and sadistic behavior and Shin’s gentleness and reluctance to hurt others.
The fear that Shin displayed when he and Eshros fought Zatch and Kiyo implied that they had little to no experience in battle. Despite this, they did enough training on their own that Eshros had eight spells at his disposal, far above the average for demons at that stage of the battle, and Shin was shown to know what each of the spells did.
Growing up, Shin was a shy boy who was picked on as a child. Eshros is a manipulative Mamodo who twists advice given to Shin by his late mother to convince Shin to destroy the places where Shin was bullied.
Shin befriends Zatch when he stops Naomi from bullying him. He and Eshros walk around the city, where he was raised as a boy and is followed by Kiyo and Zatch who believe he is a mamodo. He reaches his old school, where he was bullied constantly. He learned from his mother that he must make his own decisions and to never let anyone tell him what to do. Zatch and Kiyo overhear Eshros convincing him to destroy his old school to relieve his pain. When Shin agrees, Eshros says he is finally able to make his own decision. The next day, Zatch and Kiyo are at the school to protect it, when Shin and Eshros come. Eshros forces Shin to fight them. The battle ends in a defeat for Zatch and Kiyo, but Shin, realizing Eshros's bad deeds and that Zatch and Kiyo share a bond that he and Eshros do not, allows the battle to continue in order to prove his strength (this time forcing Eshros into submitting to his command). Though they are victorious, Shin allows Zatch and Kiyo to burn his book, content with having shown fulfilled his late mother's wishes.
During Zatch's battle against Clear Note, Eshros is seen supporting Zatch along with other mamodos. He also seen in a picture with all mamodo pictured by Zatch given to Kiyo, with his true face shown.
"Here you go. *Gives the book to Kiyo* This is the book I'm getting rid of."
"You, be quiet! You're an evil kid who deliberately deceived me! And this book is evil as well! I'm getting rid of it and I'm through listening to anyone trying to get me to do evil things! My will is too strong."