
The Nakagin Capsule Towers were designed out of a necessity to provide sleeping arrangements to a large number of commuting workers (who would leave for home on the weekends) on an extremely small site.
Each capsule, though tiny, is a fully equipped bedroom with bathroom facilities and workspace.
The idea is that each capsule would be connected directly to a central core tower that would provide support and internal movement from ground to capsule.
Structurally speaking, unlike Habitat, the capsule would "hang" from the core rather than be supported by the capsules beneath it.
While this arrangement might be terribly uncomfortable and alien by Canadian standards, the Japanese appear to have accepted it as a normal part of having to work in the city while living far outside the city. Perhaps it is the knowledge that one does not live permanently in the tower that allows it to succeed.
One advantage of the system is that it allows great flexibility in terms of the size and capacity of the tower. If only a few capsules are needed, then that many capsules will be added. If more people need the services of the tower, then more capsules will be added.
Another aspect of the tower is its understanding of its modular parts: There are the capsules, and there is the core tower. The capsules are like pockets, used privately by individual people, and are necessary in the sense that people entering the tower enter for the purpose of arriving at one of the capsules. The core tower constitutes the central movement space, used publicly by all the inhabitants of the tower. It is not the purpose of the tower, but it is used by everyone and must be in place before the capsules themselves can be attached, opened and used.
While the Capsule Towers do not use the core as a space for socialising, it might have the potential to become just such a space. Below is a sketch of the layout of the Activist branch of my project concerning the Environmental Headquarters in Quebec City. Each office, like a capsule, is there by necessity as the objective of each person's entry into the area, while the gathering space is common all the users. The important thing, of course, is to limit the number of offices or capsules attached to each gathering space, lest it get overwhelmed and become unused due to embarrassment at the crowds. There is a fine line here between a semi-private gathering space and a public corridor.

Source:
Ross, Michael Franklin. Beyond Metabolism. New York: Architectural Record Books, 1978.