Though Riku Replica was a fake, he cared deeply for Naminé. His memories of her though were a fake; implanted by Naminé under the orders of Marluxia.

With Riku Replica in play, the organization could lead Sora deeper within the castle. But with Riku having those memories, it lead to many problems with Sora. The two saw each other as rivals for Naminé attention and even self-proclaimed protectors for her. Every time the two saw each other they fought over the fake memories that were slowly taking them over.

At the twelfth-thirteenth floor interlude, Naminé was about to tell Sora the whole truth but Riku cuts in saying Sora's memory is just a trainreck and a fake. When Riku was about to finish Sora off, Naminé begs him to stop, but he doesn't listen. Right at the exact moment he was about to attack, Naminé yelled at him to stop, all the way to the point that she had to smash his heart as Larxene stated.

At the time when Marluxia took Naminé as a hostage in the last floor, Riku Replica comes back and attacks Marluxia freeing Naminé. Though his memories were a fake, he still felt that he had a duty to protect Naminé because it was his promise to her.