The series centers on Sora's search for his friends and his encounters with various Disney and Final Fantasy characters along the way. Players primarily control Sora, though there are numerous characters that join Sora's party as computer controlled members. The majority of the characters were introduced in the original game Kingdom Hearts. Subsequent installments Chain of Memories, Kingdom Hearts II, 358/2 Days, Birth by Sleep and coded featured several new original, Disney and Final Fantasy characters while the most recent game Dream Drop Distance introduces several characters from Square Enix's The World Ends with You.