It is a relatively small room with thirteen doors arranged in a circle around the centre. The top door is set slightly farther from the centre than the others, and leads back to Madotsuki's Dream Room.
The other 12 respectively lead into the top-level worlds known as the "original locations".
Clockwise from the top, they are:
- The Number World
- The Neon World
- The Shield-Folk World
- The Candle World
- The Eyeball World
- The Graffiti World
- The Mural World
- The Snow World
- The Dark World
- The Puddle World
- The Block World
- The Forest World
There are many locations that cannot be reached directly from the Nexus, known as the "deeper locations". They can only be reached by travelling through the original locations, with some locations requiring the player to traverse through many worlds before they arrive.
All of the original locations have doors and portals leading deeper into the dream world, so dead ends are rare to find in Yume Nikki. It is also notable that many locations are joined together by other worlds, so the 12 original locations are not completely separate. It is quite possible to return to The Nexus by a different door to the one you left from.
The Nexus is the only room where Madotsuki's effects can be dropped. This is done by equipping them and pressing 5. This removes the effect from your inventory, but it can be retrieved by interacting with the egg.
Each effect appears as a unique egg that is analogous to the effect it contains, for example the Medamaude egg has an eye on it, the Midget egg is small and the Neon egg strobes bright colors.
Wherever the eggs are placed, they will arrange themselves into their correct positions when Madotsuki leaves and re-enters the room. When all 24 effect eggs are in place, they make two full concentric circles around the centre. This produces a change in the real world, allowing the player to end the game.
- Strangely, the Number World Door makes a different sound to all the rest. All other doors click when they shut, but the Number World door makes a heavier thud. This is most clearly heard when travelling back to the Nexus from the Number World. This seems to highlight the Number world as more significant. Directly through this world is the corridor that leads to KyuuKyuu-kun's staircase. In the corridor, the Nexus' floor pattern can be seen as the scrolling background, and the door at the top of the staircase is identical to Madotsuki's Bedroom door.
- The Nexus is one of the few locations in the game that has no background music, which draws the player's attention to the sound of Madotsuki's footsteps instead.
- In v0.04, the Nexus' background was colored a very subtle blue instead of black. The effect eggs were also arranged differently in the center, as there were only 20 effects prior to v0.05.