Nostalgia Is Key… and Fun

His heart was banished to the realm of darkness and he was still able to stop Ansem from using his body to hurt Kairi.

He fought for years to overcome the darkness, but succumbed to it without regret to wake Sora up. Think about that-- he surrendered his bodily autonomy to the source of his trauma, just for Sora.

Even Riku Replica, who fully understood that his loyalty to Naminé had been manufactured, made protecting her his top priority. When the time came to take back his vessel in KH3, he took it to Radiant Garden so Naminé could be reborn instead.

In a way, you can see Keyblades as the symbol of Riku's love. His Kingdom Key became Sora's because his heart belongs to Sora. He saw Kairi's desire to protect others and drew out her latent potential to give her a chance to.

I suspect that the broken 'Way to the Dawn' Keyblade that Riku gave to Riku Replica will be inherited by Naminé the same way. His will to keep her safe is half the blade. She'll have to restore the rest of it with her own heart. But Naminé is a perceptive girl, so I know she'll get the message: "I love you, and I believe you can forge your own path now."

@ragingballofanxiety and @paopukairi asked:  

I just wanted you to see. You always make the right choices. On the road ahead, more than one truth will come to light. You'll forget things, lose things that you care about, and it won't always make sense. It'll be frustrating, and it'll make you angry. It may even hurt so badly you'll feel like you're about to lose yourself. But don't worry, Sora. That won't happen to you. You won't let it. You're like a sponge. No matter how much pain they throw at you, you'll suck it up, and leave things a little bit better. Just follow your heart, and you can change the lives of not one, but many. You don't have to do anything special. Just do what you do---be yourself. After all, that's what you're good at. Do what feels right to you.

Riku as the "Angel with a shotgun" nightcore girl