While he has yet to make an appearance in the ongoing Solo Leveling anime, Beru is an important character in the series. He is one of Sung Jin-Woo's oldest and most loyal companions, and he has fought countless battles alongside him.
Once seen as a terrifying threat to mankind, Beru is undoubtedly a strong character who was easily able to overpower some of the strongest S-Rank hunters in his first appearance. Given the current pace at which A-1 Pictures is adapting the manhwa, fans might get to see him make his debut in the anime sometime in the latter half of a potential season 2 or early season 3.
Explaining the origin of Beru's character in Solo Leveling
In the Solo Leveling manhwa, Beru's character appears much later on in the story, during the Jeju Island arc. He is the shadow of the Ant King, who was defeated by Sung Jin-Woo and given the name 'Beru' by him.
During Solo Leveling's Jeju Island arc, Japan and Korea joined forces to send in their S-Rank Hunters to raid Jeju Island and finally put an end to the deadly ant monsters.
For many years, the ant monsters of the infamous island have plagued the Hunters and were considered to be the bane of humanity's existence. As such, the Hunters tried to rid the world of the ants several times, as they had conducted three previous raids on Jeju Island. However, they were unsuccessful all three times in their attempts and suffered massive casualties.
The fourth Jeju Island Raid saw some of the strongest Hunters of Japan and Korea band together. However, they were put in an unexpected and terrifying predicament when the ants revealed their strongest weapon against humanity - the Ant King.
The Ant King was seen effortlessly taking out the S-Rank Hunters one by one, which filled the remaining Hunters with an impending sense of doom, as they soon realized that they were no match for the Ant King. Even Goto Ryuji, the strongest S-Rank Hunter of Japan was effortlessly taken out by the formidable monster, who was on a mission to find and kill the 'King' of humans.
Fortunately for the remaining Hunters, Sung Jin-Woo stepped in to save the day once again. Although he had previously decided to sit this Raid out since his mother had just recovered from the Eternal Sleep disease, he ultimately changed his mind when he discovered the existence of the Ant King.

After arriving at the scene and confronting the Ant King, Jin-Woo showed no signs of fear or hesitance, as he confidently took on the monster who annihilated the rest of the S-Rank Hunters.
As the two engaged in a fierce battle, the Ant King came to realize the overwhelming difference in their abilities as he noticed that none of his attacks proved to be effective against Jin-Woo. In the end, the latter ended up defeating his opponent with relative ease and proceeded to extract his shadow and add him to his shadow army.
However, Jin-Woo was surprised to see that the shadow could talk to him, which he eventually figured out to be a result of his high ranking. He eventually decided to name the shadow 'Beru' after Bernard Werber, a famous author of a novel named Empire of the Ants.
From thereon, Beru became one of Jin-Woo's most trusted shadow soldiers in the Solo Leveling series. He was fiercely loyal and protective of Jin-Woo, whom he addressed as his King. Both of them went on to fight several battles together, with Beru often showing a calm and relaxed side of him during most of his appearances. He holds Jin-Woo in extremely high regard and is prepared to attack anyone who dares to insult his King.
Final Thoughts
After being turned into a shadow soldier, Beru quickly became one of the most popular and beloved characters of the Solo Leveling series. Fans are extremely fond of his relationship and admiration for Sung Jin-Woo, as they get to see a more lighter and humorous side of Beru during their interactions.