The protagonist and player character of Avalon Code. Yumil (ユミル Yumiru) has been assigned the task of recording everything around him in the Book of Prophecy, becoming its new Chosen One in title. As such, he becomes gifted with the ability to read ancient runes; see and interact with Metalize (Recipe) Tablets, ghosts, and the Book Spirits; use any armament or equiment produced from the Book; and change the makeup of anyone or anything recorded in the Book. At one point in the game, he is given the choice to align with one of four legendary Weapon Schools.
Although Yumil begins the game under the protective wing of fellow slum-dwelling pickpocket Rex and is seen to correspond frequently with the sickly townsgirl Fana, his past—including reference to any family members deceased or living—is largely left unelaborated. However, it can be assumed that he continues to live on with the Spirits in a home in the New World.
Judging by dialogue clues dropped by other characters, Yumil is a native Kaleilan of approximately fourteen or fifteen years. He is of middling height and wears his auburn hair in what could be described as an unattended bowl cut. His eyes are haze and quite large.
He wears a signature olive embroidered justacorps, striped jacket, white long-sleeved undershirt, honey-colored breeches which may or may not be of the real-life Spanish style , white tights, and dark leather shoes with sizable buckles.
For accessories, he also has a golden yellow ascot, gold-tasseled leather satchel worn on the left side, and leather pouch clipped to his belt. His character design does not incoporate the quatrefoil motif in any way, though the aforementioned satchel fastens with a puzzle piece design reminiscent of the Book of Prophecy's cover and unique to him. It is unknown to what extent his dress reflects his station in life.
- "A boy who takes any challenge head-on. The main character if the player chooses to be male. He has an easygoing personality but will always take a firm stance when the situation calls for it."
- - Avalon Code official English instruction booklet
Because Avalon Code puts the player's choice of hero to use in mostly aesthetic ways, the events of the story--including the main character's actions and reactions--remain exactly the same whether running the campaign as Yumil or Tia. This is not to say that he lacks character. Though he values justice and exemplifies generosity, his sense of responsibility is his defining feature,
His precise life circumstances are left extremely ambiguous by the writers; he is presumed to have carried on a quiet existence in the poor district of Rhoan Town for all his life, and a solitary one for most of that time. Not unusually, he tends to function on a microcosmic level, as evidenced by the extensive writing projects (letters to Fana and a high fantasy novel draft) scattered around his ramshackle dwelling. However, while he comes off as a hopeless dreamer to some and an unmotivated truant to others, he is extremely aware of her surroundings, majestic or mundane. It is likely that both this attention to detail and penchant for describing the world for the benefit of others factor into his eligibility for Chosen One.
On an interpersonal level, though he apparently did not stray far from home prior to the beginning of the plot, Yumil is largely unafraid of "rubbing shoulders" with others on any level of society. He treats his world-renowned combat teacher the same as the misunderstood town witch, and neither pities himself for being poor nor shuns the rich for being on the opposite end of the spectrum. While he is wronged by both his thieving friend and the accusatory monarchy, he does not label them as "bad" people or try to change their questionable ways.
Despite his tendency toward trust, he can also be blunt--even cutting--when it comes to others' feelings. Additionally, depending on the player's reaction choices at key points, he may begin to externalize the results of the unfair treatment he recieves and the trials he undergoes.
Yumil is portrayed as a silent protagonist, although the dialogue of the characters with whom he interacts strongly indicates that he is fully capable of normal speech. Interestingly, he is unable to view his own Book of Prophecy profile (likes/dislikes, aspirations, and personal history). In-game, his page is used to show the player's current status, including hit point and plana point totals, equipment, and inventory.
If the player chooses Yumil as the protagonist, Tia, his female counterpart, will never be encountered in the game.
- Yumil's age is the cause of some confusion among fans of the English localization, as Grandpa Vis ambiguously states at the beginning of Chapter 5 that the decennialy-occurring Tournament which happens in the game will be his "first".
- Yumil's name uses the same Japanese characters as does that of the important Norse mythological figure Ymir. The two do not share any other notable characteristics.
- Though the speed of the action remains the same for the sake of gameplay, there is a notable visual difference between Yumil and Tia 's running gaits, Code Scanning leaps, and somersaults.