Unruin nearly kills Fuuko, he's inmortal and has lived through multiple resets like Undead. Also he's a vampire.
Juiz decides to go all in on having Fuuko defeat god, so she makes a deal with some moon deity to save her. The deal required sacrificing all her points. These points were mentioned when Andy and Fuuko joined the Union and never again; the points determine the order of the seats. Having no points lefs this late into the game means she won't be able to use the ark.
Andy and Fuuko jump one week ahead thanks to the deal, just in time for the quest reward. The reward included the addition of uma Ghost, so now people who die can exist as ghosts. Fuuko is now a ghost and they have to save her soul from uma Ghost.
The penalty for failing was the addition of uma Revolution. With uma Revolution, planets orbit around stars. Presumably, the idea behind that penalty is that the Earth was not rotating around the sun so, as soon as that rule it's added, the Earth starts falling. Juiz thinks they have been penalized but they haven't. However, the earth lost 3 of it's seasons. In the real world seasons are the result of the earth orbiting the sun, so a world without seasons would be a world which doesn't orbit the sun. By god's logic, having no seasons in a world without Revolution should be the same as not orbiting the sun in a world with Revolution. The result is that they fall to the sun either way.
TL;DR: The rules in this universe are made up by god, so he set up the 100th quest so that they'll die either from the laws of physics or from the law of nonsense physics. They're currently going to die by nonsense physics.