|“||You're all I need, Marie!! What do I care about other people?!||”|
Gauche is a tall, slender built young man with light skin and shaggy light brown hair that drapes over his forehead and left eye. He has brown eyes, while his left eye has been replaced by a small magical mirror.
He wears a long-sleeved blue and purple shirt under a brown short-sleeved shirt, light brown trousers tucked into brown trench boots. As a member of Black Bull, he wears the official black robe of his squad: black with golden lining and the Black Bull's insignia over his left pec.
As a prisoner, Gauche wears a striped long-sleeved shirt and matching pants.
Gauche is depicted as a brash and brutal individual. He cares greatly for his sister Marie and is shown to get extremely jealous when she takes a liking to others(a good example being Asta). Many characters have noted that his love for his sister is rather obsessive and is thus nicknamed "sister lover". He acts to others in a cold and ill-mannered way and does not hesitate to attack anyone that gets in his way regardless of age or gender especially to Asta as he always threatens and attacks him because of how his sister has taken a liking to Asta stating that she would like to marry him one day. Early in his introduction, Gauche did not care for anybody but his sister even forsaking Sister Theresa, his comrade and the children in order to escape with his sister (though he did turn back only after being persuaded by Marie). This later changed however as he showed consideration for Sister Theresa's well being and used his magic to help and assist Asta in their battle against Sally (this being the first time he used magic to help anyone but himself).
Gauche was born as the first son of House Adlai. Sometime after the birth of his sister Marie, their parents die in an accident, and another noble inherits their wealth and casts out Gauche and Marie. Gauche does everything to protect Marie, killing and stealing as needed.
When Asta arrives at the Black Bull headquarters, Gauche is adoring his little sister. He yells at the others for their behavior. Upon seeing that Yami has returned, he goes to ask him if he can go see his sister, but Yami has everyone sit and listen to the new recruit's introduction. Gauche then joins some of the others on a couch outside to watch Asta's initiation, and afterwards he warns Asta to stay away from Marie.
After Gauche finishes defeating a group of bandits, he shares with them that it is his little sister's birthday. The notion of visiting his sister brings so much joy to him that his nose bleeds. Afterwards, with bags full of toys, he travels to Nairn. However, to his dismay, he finds Marie playing with Asta. Gauche immediately confronts Asta, who finds no qualm in his act. Subsequently, Marie also asks her brother to stop hurting her future husband, which quickly breaks Gauche's heart and body to pieces. The turn of event prompts Gauche to try killing Asta, until Sister Theresa, who is in charge of Marie's well-being, arrives to take Marie back to the church. After a series of arguments between Gauche and Theresa, Marie leaves with the latter as Gauche is unable to stop them. The two Black Bulls decide to spend the night at Rebecca's house after she offered.
That night, while Asta is fast asleep, Gauche enters the young Knight's room and prepares to kill him. Unconsciously, Asta manages to avoid the first attack, which leads to a stalemate where Asta tries to parry all of Gauche's attacks. However, when Gauche creates a clone of himself, Asta is pushed outside where he finds the town is covered with snow. As Gauche is still determined to kill him, Rebecca comes to Asta and informs him that her siblings are missing.
The moment he learns that his sister was also kidnapped, Gauche quits his attempt to kill Asta and confronts Theresa. Fortunately, Asta manages to prevent Gauche from harming an elderly woman and forces Gauche to calm down by hitting him. After he calmly threatens to kill Asta, Gauche remembers about the mirror that he gave to Marie and could use to trace her location. After Asta convinces Rebecca of her siblings' safety, Gauche leaves with Asta and Theresa. Noelle tries to come with them, but Gauche orders her to stay.
As they reach the cave where the kids are held, they notice Marco Scarlet outside the cave, but Gauche refuses to stop as his priority is his sister. He leaves Asta and Theresa and goes in alone. When he finds Marie and sees she has a bruise on her cheek, he gets angry and attacks Neige, who tries fighting back using his Snow Magic but is overpowered. After destroying more Snow Friends, Gauche is captured by Neige. Gauche's clone then hits Neige from behind and frees the original, who begins kicking the defenseless Neige, despite Theresa's and Marie's pleas from him to stop.
They are all surprised when Sally arrives. Gauche attacking her, but she easily redirects the attack with her Gel Magic. Gauche tries with multiple beams, but Sally is still protected by her Sticky Salamander. After Sally turns Baro into a mud monster, Gauche takes his sister and flies away, abandoning Theresa, Asta, and the other children. Marie demands that they go back, but Gauche refuses because he would not be able to protect her. She punches him and tells him that she hates when he is like this, and that she likes him for being a Magic Knight who protects others. They encounter Marco at the cave entrance, and Gauche leaves Marie in his care.
Returning to the fight, Gauche expects Asta and Theresa to have run off themselves and is surprised to see them still there, calling Asta a fool. Gauche flies in and kicks Asta, saving him from the monster's attack. He decides to attack Sally and the monster with his clone, but even his doubled attacks are not strong enough. While thinking about his trump card, he is knocked down by the monster. He is then saved by Asta, who criticizes him for attacking by himself. Gauche decides to protect and support Asta, which prompts the Demon-Dweller Sword to emerge filled with Gauche's mana. Asta swings it, releasing a flying slash, but the monster still regenerates. Gauche then develops a new spell but realizes that he does not have enough mana, so he asks Theresa to buy him some time. Gauche then uses the mirror in his left eye to multiply Asta, who release multiple flying slashes, destroying the monster and Sally's salamander.
When Baro rises again to attack Asta, Gauche panics because he is out of mana, but Neige saves the boy. Suddenly Neige and Gauche are struck down by Licht, who avoids hitting Gauche's vitals. Theresa tries to protect everyone, but she too is struck down and Gauche calls out to her. After Yami and Finral Roulacase arrive, Gauche crawls towards Theresa and demands that she does not die. Finral then transports the children and the injured to safety.
Gauche is leaning over Theresa's bed as healers see to her injuries and another sees to his. He shouts at her not to die, and she tells him to shut up and gives him the rest of her mana so that he can help Asta. Following her example, the children, Neige, and Marie offer Gauche their mana. Gauche tells Finral to take them back to the cave, but Finral refuses so Gauche asks nicely, bowing his head. They return to the cave as Licht is preparing Light Shaft of Divine Punishment. Gauche quickly summons a mirror and appears in front of Yami and Asta. Using his left eye's mirror, he then summons a giant mirror, which reflects Licht's spell. Yami congratulates Gauche on defeating Licht, although both are confused when Licht admits to not wanting to hurt Gauche.
Shortly after, the Third Eye appear and Yami is forced to protect his men. Amazed at their strength, Gauche realizes how far below them he is. When Jack the Ripper, Nozel Silva, and Charlotte Roselei arrive and save the Black Bulls, Gauche asks Finral who they are. The pair are astonished by the captains' fights.
After Asta hits Licht with his Demon-Slayer Sword and releases Licht's sealed mana, Finral panics and Gauche tells him not to give up. The Third Eye then seal Licht, gather Valtos, and retreat, and the Black Bulls gather around Asta who collapses from exhaustion.
Gauche visits Theresa who is still recovering and the two bicker until Marie asks them to stop. Gauche thanks Theresa for taking care of Marie and mentions that he is glad the sister survived. Marie then perks up when Asta arrives, which angers Gauche. After Rebecca kisses Asta, Marie wants to do the same and Gauche tries to kill the boy.
Some time later, Gauche joins his teammates at Raque for a mission to the Seabed Temple. While at the beach Gauche shows his sister the beach through a mirror and even attacks Asta when his sister wishes to enjoy the beach with Asta. When Yami shows up, Gauche and the others are punished for causing a ruckus by being buried up to their heads in the sand. Gauche then listens as Yami explains about the Seabed Temple and how they are going to get their. A week later on the night of their departure, Gauche joins the rest of his squad in encouraging Noelle to do her best. After Noelle has managed to gain control of her mana, the Black Bulls enter Noelle's spell and head to the Seabed Temple. When they reach the temple, Gauche and the others are guided to meeting Gifso.
After meeting with Gifso and learning that they will have to play a game to obtain the magic stone, the Black Bulls, except Yami, and the priests are transported to another location. Once divided they listen to Gifso explain the rules, and afterwards is confronted by a priest. Gauche easily manages to defeat the priest, and says that he will end this game then go meet with Marie. Once members of the Eye of the Midnight Sun arrive, Gauche is confronted by one to their members. During the battle Gauche which places with Grey and manages to defeat the guy while Grey distracts him. Afterwards Gauche carries Grey to find some more enemies to face when they come across Charmy. Suddenly Gauche and Grey are caught in a trap and confronted by an enemy. As Gauche thinks about what to do, he tells Grey to transform a stone into a large of meat while he shout that the enemy is after her food to Charmy. After Charmy manages to defeat the enemy, Gauche wonders about how they can use Grey's ability to defeat the enemy but notices that Grey transformation is coming undone. Gauche is shocked to find out that Grey is a woman and decides to relax and look at a picture of Marie since he can't move.
Gauche then accompanies both Charmy and Grey to confront Vetto but is too late as Vetto was defeated. Later Gauche is in the same as most of the Black Bulls resting. Gauche complains about how they have to spend the next day at the Seabed Temple since Finral used to much of his mana. When the temple's citizens show up to cheer for the Black Bulls, Gauche is surprised by this and expresses how he wants to see Marie. After a while Gauche wonders how much energy does the citizens have since they have been cheering for a long time. The next day Gauche leaves the Seabed Temple with the rest of the Black Bulls. Once back at the Black Bulls headquarters, Gauche is with everyone in the common room when he points out that Gordon is sulking in the corner.
In search of a cure for Asta's cursed broken arms, Gauche and Gordon Agrippa research curses in the royal library. However, they return unsuccessful and transformed into otakus. Asta reveals that his arms are healed, and Gauche and Gordon threaten to re-curse his arms. Gauche later decides not to attend the Star Awards Festival.
A few weeks later, Gauche is waiting to take any mission requests while Grey and Gordon try to socialize with him. However, they are interrupted when Rades Spirito, Sally, Valtos, and an army of corpses attack the Black Bulls base. Gauche blasts them back with Reflect Refrain and confronts the members of the Eye of the Midnight Sun. Gauche demands to know why they are attacking, to which Rades replies that they are after the magic stone. Gauche attacks Rades but Sally redirects it with her gel and reveals that they are not allowed to kill Gauche.
After Grey transmutes Sally's gel into crystal, Gauche is able to destroy the salamander. Rades then summons No.0 - Michael Caesar and easily defeats the Black Bulls, with Gauche shocked that it can use two different elements simultaneously. Gauche wonders what they can do, so Gordon and Grey tell him not to give up. Gauche resolves to make an exception and protect others besides Marie. Rades prepares to attack again but is stopped when an alarm sounds from the base.
Shocked by Henry Legolant's sudden appearance, Gauche demands to know who he is, but becomes frustrated with Henry's slow speech and interrupts with more questions. After Henry moves his room out of the way of Rades' attack, Gauche realizes that Henry is the base's "ghost" and the one who rearranges the layout. Having failed to hit Henry, Rades tries to attack the other three, but Henry moves part of the base into the path of the attack, defending his squadmates. Henry introduces himself and promises to hurt those who hurt his friends. The other Black Bulls are shocked to see the base rearrange into a giant bull and how recklessly it fights.
When Sally manages to topple the base, the other Black Bulls come to Henry's defense, with Gauche multiplying Grey so she can transmute the gel again. Rades tries to take advantage of their distraction, but the freed Henry defends them and defeats Michael Caesar. As the Black Bulls celebrate their victory, Valtos reappears and then disappears with the other Eye of the Midnight Sun members. Afterwards, Gauche questions if the base can be fixed.
When a bright light shines on the horizon, Gauche wonders if it is another attack before he begins glowing brightly himself. Possessed by an elf spirit, Gauche turns on his squadmates and summons several magic mirrors.
- Mirror Magic: Gauche uses this form of magic to cast mirror-based spells using a mirror, like reflecting light or creating mirror copies of something.
- Mirror Magic Tool 「鏡魔導具 Kagami Madōgu」: Gauche has a mirror embedded in his left eye socket. The mirror has the power to augment his magic at the cost of his mana.
- Asta vs. Gauche Adlai: Interrupted
- Gauche Adlai vs. Neige: Win
- Asta, Gauche Adlai, and Theresa Rapual vs. Sally and Baro: Win
- Asta, Magna Swing, Luck Voltia, and Gauche Adlai vs. Four Priests: Win
- Gauche Adlai and Grey vs. Eye of the Midnight Sun member: Win
- Gauche Adlai, Grey, and Charmy Pappitson vs. Eye of the Midnight Sun member: Win
- Gauche Adlai, Gordon Agrippa, Grey, and Henry Legolant vs. Rades Spirito and Sally: Interrupted
- "You're all I need, Marie!! What do I care about other people?!" 「オレにはマリーさえいればいい...!! 他の人間のことなんざ知ったことか...!! "Ore ni wa Marī sae ireba ī...!! Hoka no ningen no kotonan za shitta koto ka...!!"」
- His name was first romanized by the author as Ghosh Adorei but was amended to Gauche Adlai in the following volume.
- Tied with Fana, Gauche ranked 21st in the popularity poll.
- Gauche is the smartest Black Bull.
- Gauche is French for "left" or "awkward".