Kovu is a stocky lion cub with red-brown fur. He has a hair tuft of dark brown fur, the beginnings of a mane, on the top of his head. On either side, fur sticks out from his chin. His forelegs have tufts of dark brown fur emerging from them. His eyes are green, with dark rims resembling Scar's. His paws, underbelly, and muzzle are a beige color, and his underbelly doesn't extend up over his neck. He has an outlander shaped, black nose and three whiskers on either side of his muzzle.
As seen in a painting as a teenager, not much about Kovu changes except that he has grown bigger and his mane has begun to develop itself.
In Return to the Pride Lands, Kovu has become a young adult with a full mane and has a scar over his left eye, identical to his adoptive father, and former predecessor Scar. His jaw is quite small, and his muzzle color is present at the tip of his snout. His inner ears have changed color, becoming dark pink, and he now has four whiskers on each side of his muzzle.
Kovu, unlike his mother and siblings, is very relaxed, kind and friendly, and doesn't necessarily believe in their cruel and violent, evil ways. Despite this, when his mother asks him to do something, he will obey and even approach his older sibling, should he try to disobey her. He holds no animosity towards the Lion Guard, frequently avoiding confrontation with them. He is shown to be excited at the prospect of living in the Pride Lands so he could see Kiara again.
Years later, it's revealed that Kovu was manipulated by Zira into believing Simba was the enemy, which implies that he was at one point cruel and murderous, but this later changes when he befriends Simba and bonds deeper with his daughter, Kiara. His initial refusal to fight, a trait he had as a cub, is resurrected when he attempts to stop an attack on the Pride Lands held by Zira. He is willing to put the past behind him, as when he sees Kion again, he does not hold any animosity towards him for their past meeting and he later befriends him as his brother-in-law.
Kovu originally lived in the Pride Lands with his mother and siblings during the reign of Scar, who picked Kovu to be his heir. Sometime after this, Scar's nephew, Simba returned to the Pride Lands, battled Scar and defeated him, taking Kovu off the throne of the Pride Lands. After Zira tried to attack him to avenge her former leader, Simba banished Kovu, his family and several other lionesses loyal to Scar into the Outlands.
Sometime after this, Kovu met and briefly befriended Simba's daughter Kiara, but they were both later separated by their feuding parents where Zira eventually trained Kovu to overthrow Simba and take his place as King.
A while later, Kovu came across Nuka, who was pinned down by Kion, Kiara's younger brother, who had come to the Outlands to solve the problem of lions not sharing a waterhole with his hyena friend Jasiri's clan. The two brothers, along with Kion and Jasiri circle each other with Kion questioning the two on why they are in the Outlands and not in the Pride Lands, to which Nuka says that they are not welcome there. After learning that Kion is Simba's son, Kovu wondered if the King would let his family back into the Pride Lands, with the possibility that he could see Kiara again. Kion is surprised to hear that Kovu knows his sister, to which Kovu says it was a while ago, before telling Nuka that they should take Kion and Jasiri to see Zira. He agrees with a sinister tone to his voice, and he and Kovu lead Kion back to their mother, Zira.
Kovu excitedly informs his mother that their visitor is Simba's son Kion and waits to see what his mother has to say on the matter. When the conversation turns to Kion's ability as a leader of the Lion Guard, Kovu's curiosity is piqued and Zira starts to reveal her knowledge of the Roar of the Elders. He is shocked when he learns that Kion can conjure water from using his Roar on a nearby cloud. Eventually, his mother drags Kion away from everyone to speak with him in private, leaving him alone with his sister Vitani, Nuka and Jasiri with an order to play nice.
Later, Nuka becomes antsy over his mother's absence and attempts to strike Jasiri. Kovu leaps between them, urging him not to start anything as per their mother's words. Jasiri laughs at him, assuring him that she can play any game Nuka wants much better than he can. Just as Nuka pounces, Zira returns, much to Kovu's delight. Kovu then watches his mother force Jasiri out, claiming that Kion has sided with the lions. Zira then leads her children back to Kion.
Kovu becomes confused when he sees that Kion has been cornered, and asks his mother why they can't be friends. His mother tells him that Kion made his own choice to side with the hyenas and that it is his fault. When Nuka voices his concern over the Roar, Zira explains that Kion cannot use it against them since using it on lions was how Scar lost it all those years ago. Zira then offers Kion one final chance to side with her, but Kion notices Ono flying overhead and calls the Lion Guard together. Kovu becomes fearful and immediately withdraws himself.
When the Outsiders gather together again, Zira tells them to stand tall. Kovu is noticeably upset about the situation and lowers his head. Kion is then reminded by Bunga that Scar lost the Roar by using it for evil and not by using it against lions, and, despite Zira's please to listen to her, Kion unleashes the Roar on all the Outlanders. Kovu quickly dives out of the way and shields himself, missing the impact entirely. When the Outsiders vanish over the canyon, Kovu looks toward Kion, who glowers back at him. When he moves a step towards him Kovu runs after his family, calling for his mother to wait for him.
When she and the rest of the Guard return to the Outlands, Anga spots Kovu standing on top of Pride Rock. When Vitani and her Lion Guard see Kion's Guard, they start to fight, but Kiara and Kovu come to break it up. Kiara explains that the Outsiders have joined Simba's pride. Vitani, not noticing that it's Kion, Kiara's brother, says that it's been a long time since she's seen him. Kovu asks what's going on. Bunga asks the same question. Kion returns to Pride Rock and his family. They all explain to him and the rest of the Guard what happened while they all were away. That's how the lion guard learns about Zira completing her way in the circle of life. After having heard what happened Simba announces that Kiara and Kovu will be the future Queen and King of the Pride Lands.
Kovu is later seen that night on Pride Rock as the spirit of Mufasa watched over the united family, before fading into the clouds. Kovu walks into the cave for the night whilst Kiara stays on the peak having a conversation with her brother.
The next day, he is present during the battle of the Lion Guards, in which Kion abdicates his position as leader of the Lion Guard to Vitani, who, in turn, gains the Roar of the Elders, much to Kovu's amazement. Kovu, along with the rest of the Pride Landers watch Kion leviate Pride Rock with the Roar.
Sometime later, along with the rest of the royal family and other Pride Landers, Kovu watches as Kion becomes King of the Tree of Life and mate of Queen Rani.
In a news article, Kovu is noted to be a descendant of Scar. This is incorrect, however, as Zira was only Scar's devoted follower. However he was at one point meant to be Scar's son in an early script for The Lion King 2: Simba's Pride, but this got scrapped as this would have resulted in an incestuous relationship with Kiara as first cousins once removed. The director later described Kovu as an orphan, in which he would've been Zira's adoptive son, unrelated to her and Scar.
If Kovu was Scar's son, he would've been the first cousin once removed to Kion as well as Kiara.
As both a cub, and a young adult in the series, Kovu is voiced by Jason Marsden, the same person who solely voiced young adult Kovu in The Lion King II: Simba's Pride.
Kovu got his scar from Zira after the death of Nuka in The Lion King II: Simba's Pride.
Interestingly, how he got his scar is never physically explained in the final episode.
Kovu is one of three lions in the The Lion King franchise to have a scar over his left eye, the others being Scar, and Kion. Out of all three of them, he is the only one to not have it inflicted by a cobra, instead being inflicted by his mother, Zira. She did it, because she blamed him for Nuka's death in the ambush against Simba and enraged with fury Zira scratched Kovu across the face.
Chronologically, he is the fourth lion in TheLion King franchise to aquire a scar, the first being the strange lion who attempted to overthrow Mufasa before being killed by the King's brother, the second being Scar himself, who recieved it years before the events of the original film, and the third being his brother-in-law, Kion, who received his scar after Kiara and Kovu's first encounter, but before their re-encounter as young adults, as Kovu received his scar presumably during the Lion Guard's journey back to the Pride Lands.
Ironically, Kovu becoming King of the Pride Lands by marrying Kiara, the future Queen Regnant of the Pridelands, was actually the ruling (and the supposedly dying wish) of Scar, but it would not fit up to Zira's plan of Kovu overthrowing Simba and Kiara.
Though Kovu bears a scar over his eye, his does not count as the Mark of Evil , due to the fact that he didn't acquire it from a cobra bite.