Friends and Subjects
The link between friends who avoid becoming heartless and heartless friendless people begins in Deep Jungle with Tarzan's talk of "ei ooh ooh ooh ah" which somehow translates to either 'heart' or 'friend' or possible both.
Jane: Oh, no I've got it. "ei ooh ooh ooh ah" means heart. Friends in our hearts.
Sora: Oh, so that's what it meant.
Tarzan: Friends same heart. Clayton lose heart. No heart no see friends. No heart no friends.
Clayton lost his heart as he had no friends; Sora is strong because he has friends. This logic is extended through the Coliseum world where Sora proves his heroism in battle and claims his friends are his strength. For the majority of the first game friends themselves are considered strength in a more social aspect of being.
(Tarzan, Heart and Friends)
(Strength of Heart as Friends)
Chain of Memories clarifies the intricacies of the divide between individual and social, loner and group, friends and memory. The game begins with Sora entering 忘却の城, Castle Oblivion. Oblivion in some situations is equal to forgetting, but one irony that comes out through the story is that while translationally it works, the creators' understanding of memory works in a completely different way. Not a matter Oblivion. Sora's journey involves him interacting with memories of his friends. He slowly forgets his friends, particularly Kairi, and remembers Namine. The game's conclusion posits several things: a) Sora protects his friends regardless of whether their based on true or false memories, b) Sora's memories of his friends are too strong to be fully erased, and c) peoples hearts are tied to each other through memories. Essentially, Sora represents the social subject who lives and survives through his ties to others. The chains of memory are not shackles, but links that help and protect.
(Namine explains Heart, Memory, Chains and Friends)
Simultaneously, but unknown to the player until the end of Sora's voyage to the 13th floor, Riku enters the same castle from the basement and travels to the 1st floor where he leaves from the entrance. Like Sora, Riku visits worlds the player has previously experienced, however, many of these worlds were never visited by Riku in the first Kingdom Hearts. That said, the logic given is that he abandoned his home, family and friends and took on darkness. As such, he encounters only creatures of darkness.
(Only dark creatures throughout Riku's journey)
(Riku's memories are empty because he gave up family and friends)
Riku climbs up the castle, basement through empty floors until he reaches the memory of his home islands. At this point he finds shadows of his friends who disappear.
Whereas the previous floors represent his individual, independent nature, Destiny Islands shows his abandonment of sociality. At this point Sora and Riku are simply two extremities, the social and the individual, what one might claim as the extreme Social and Individual subjects. There is of course a connection here to the Japanese social subject and the American individual subject. However, the conclusion of Riku's story indicates the necessity of the social. He requires Mickey's assistance. This is repeated in the conclusion of Kingdom Hearts II where Riku, who went solo, gave himself to darkness and took Ansem's form in order to help defeat Organization XIII, rejoins Sora and company and ultimately defeats Xemnas together with Sora. Like the typical reliance of a team of characters in Japanese RPGs opposed to the solo hero of Western FPS games like Doom, Kingdom Hearts ultimately falls on the side of the social subject. People are dependent upon the social, on friends.
(Riku wants to fight alone, but needs Mickey's help)
(Riku as the individual subject eventually teams up with Sora to defeat Xemnas)
Now we come to the concept of connections and ties. Worlds are tied to darkness; hearts are tied to each other and light. Some ties are explicitly good, but others are bad. Those that are good are between people, those that are bad are between worlds. Worlds are to remain separate and separated, but people must be connected. Within a transnational aesthetic the world order/border must be maintained, but the people must be connected through heart/memory.
(Ansem connecting the worlds through darkness is 'bad')
(Being connected to people is 'good')
Finally, in Kingdom Hearts II there is a third form of connection that is acceptable: commodity connections. These commodity connections are what Sora and company use to travel between the worlds. It is no longer the worlds themselves that have keyholes and passages, but items in/of the worlds, commodities, which connect.
(New Commodity Connections - Hollow Bastion Restoration Committee Card)
(The Land of Dragons - Sword ; Twilight Town - Sea Salt Ice Cream)