Kovu becomes affectionate with Simba's daughter Kiara after the two cubs escape from crocodiles on the Outland borders. Simba and Zira clash over this, but the two leave without fighting. Zira plots to train Kovu so he can easily kill Simba at the right moment (the "My Lullaby" song scene). Kovu was to save Kiara from a fire of Nuka and Vitani's own making so he could get closer to her and in turn, Simba. Then, when Simba was alone, Kovu would kill him.
The plan starts well, but Kiara and Kovu fall in love, which causes Zira to plan an ambush on Simba and Kovu while the two lions are out walking. Simba falls into a gorge during the ensuing fight, but escapes via a log dam piled up against one end of the gorge. The logs fall and crush Nuka, killing him. Zira pauses to mourn her son's demise, asking Scar to watch over Nuka for her, but she very quickly takes her anger out on Kovu, giving him a scar identical to Scar's. Kovu, defiant for the first time, flees for the Pride Lands as Zira declares war on Simba.
Zira rallies her lionesses and they travel to the Pride Lands for the final battle. At the battle's climax, Simba and Zira are about to fight each other when Kiara and Kovu intervene and stop the battle before it can begin, convincing the Outlanders and the Pridelanders that "they are one." Vitani is the first to realize this and switch sides. Zira threatens to kill Vitani if she doesn't come back, disgusting the other lionesses, who subsequently abandon her.
Enraged, Zira charges at Simba, stating that "this is for you, Scar." Kiara leaps into Zira's path, causing Zira to knock Kiara and herself off the edge of a nearby cliff, sending them both tumbling into the gorge. Kiara lands safely on a ledge, but Zira slides off the edge and hangs precariously onto it. Kiara makes an attempt to rescue Zira, but Zira swipes at her, rejecting help. Zira, having rejected aid, slips and falls into the river below and drowns.