In the beginning of Kingdom Hearts, Kairi begins to collect thalassa shells and make them into a good luck charm as sailors did in a legend. She reveals to Sora to ensure that she, Sora, and Riku have a safe voyage as they travel on their raft to other worlds. After Kairi's rescue from Hollow Bastion, and the return of her heart, Kairi gave Sora her completed thalassa shell lucky charm to bring him luck, but made him promise to return it to her.