Universe Contraction Day

The universe will one day expand to the extreme and start to shrink. The protagonist travels a hundred years in the future and finds that his home has been turned into a tourist attraction. I can upgrade everything! "It's him! That man is back!" "The man within the high wall, he is the patron saint of the Dragon Kingdom! He is back!" The strongest scientist in the past, DIYed all kinds of weird weapons in the apocalypse, and started building tower defenses for the city! Build the top doomsday home! Upgrade tower defense weapons! Upgrade your vehicle! This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.