Birthdate: 15th July
Horoscope: Cancer

Battler is the eighteen-year-old son of Rudolf and his first wife Asumu, and is generally considered to be the main protagonist of the series. He is extremely stubborn, and is afraid of "shaky" transportation, fearing he might fall off a boat. At first glance, he appears to be hotheaded, cocky, and even a little perverted (given the fact that he tries to grope young ladies and even his cousin Jessica several times). However, he has a heart of gold he isn't afraid to show when the situation calls for it.

Battler is also an extremely rational young man, and has an extreme talent for deductive reasoning and thinking outside the box, described as "flipping the chessboard" so that he may be able to predict the moves and motives of his opponents. Because of this, he does not believe in witches or magic. This causes some conflict with his cousin Maria, who has immersed herself in studies of the occult and believes strongly in witches, especially the Golden Witch Beatrice.

Six years prior to the start of the series, his mother died and his father remarried almost immediately. Battler had a falling out with his father, disturbed by how fast everything went, and rebelled against him, cutting all ties to the Ushiromiya family to live with his maternal grandparents for the next six years. After his grandparents died, he returned to his old home. His relatives held no ill will towards Battler for running away, save for Kinzo; in fact, Battler was able to rekindle his old relationships very quickly. However, out of fear of how Kinzo would react if it was brought up, reference to his rebellion is taboo.

The incident six years ago, however, had also caused a different tragedy altogether. Six years prior, Battler confessed to Shannon that he will take her away from the island and save her. However, due to his falling out, he never returned, leaving the stricken Shannon to live her life in hope of something that will never come. This incident had caused the pain of the Shannon personality to transfer deep into Yasu's heart, and because of that, the witch Beatrice was born.

Ironically, despite his disbelief in magic and witches, Battler has very strong magical powers. He can generate a barrier that offers him great resistance to anything magical in nature, which serves as the main contributing factor to his denial. As such, he serves as a natural enemy to Beatrice and other witches, since they draw power from those who believe in it. Battler's resistance is thus put to the test by Beatrice, who bombards his sense of logic with countless scenarios that seemingly can't be explained by human means in the hopes that he will ultimately surrender his position and accept her existence. He has in fact neared a breaking point many times, but barely manages to regain his composure and strengthen his magical defenses each time, now to the point where his barrier is nigh indestructible, a perfect shield perhaps not even gods can ever hope to penetrate.

Soon after Beatrice's death in the fifth game, Battler is banished from the Game Board after he fails to provide a counter to Erika's theory on the culprit's identity. It is in this pitiful state and limbo where Battler finally solves the mysteries of Rokkenjima and reaches the center of all truths. He returns to Game Board immediately after, and with the help of Beatrice's furniture, he successfully forms his own theory and destroys Erika's. Battler is than named the "Endless & Golden Sorcerer" by Lambdadelta and gains all of Beatrice's power as well as the position of Game Master for the sixth game against Bernkastel. His weapon of choice during debates is a golden longsword that allows him to weave with red and strike with blue. His knowledge of the truth even lets him wield a third, known as the golden truth.
In EP8's "Magic End", it turns out that he actuallly is still alive, survived from the explosion in Rokkenjima at 1986, but lost his memory due to some circumstances. Because of that, he lived with Hachijo Ikuko and receives a new name, Hachijo Toya.