...didn't you read the summaries?
Is the sky often dark when there's an earthquake?
Why did Taiouchi go away?
I think it was because he hated the sound of Tanpopo, Memetchi,Mametchi, and Kutchipatchi screaming!
...Mametchi finally succeeds in creating "Mametaiouchi", a little sun that will follow Mametchi everyone and always provide him with light. But just as this happened, the real Taiouchi (Tamagotchi land's sun) was flying overhead...
The next morning, it was dark outside. Taiouchi was nowhere to be found, and thus Tamagotchi World had no light from it's sun.
During more preparations, the Tamagotchi's were violently thrown into the air and heard a strange sound. It was soon discovered that Tamagotchi World had caught a cold. Mametchi ran to the Mame Invention Center to try to help, and overheard Mimizu kocho explaining that Taiouchi had left a note that said "I heard that Mametchi has finally succeeded in eventing a new sun. So I am going away. Goodbye." Mametchi is crushed, thinking that all of the current problems are his fault, and goes to bed without talking to anybody.
Just when all appears to have been resolved, communications are once again cut off, and a bright light appears in the cabin. From back in the Mame Invention Center, they note that the rocket has used up all of its power, and thus has no way of returning to Tamagotchi World. Everyone starts crying, but suddenly Mametchi's voice is heard announcing that they have returned! The light that had entered their cabin was that of the returning Taiouchi, who brought them all back to Tamagotchi World (Taiouchi later explained that the real reason he left was to go on a hot springs tour, adding "isn't my skin smooth now?"), and finally everyone is able to rejoice once more.