The Story of the Nation-Guarding Heir

After unexpectedly transmigrating to an alternate ancient world, he became the heir to the Duke Who Guards the Nation's estate. He had originally planned to enjoy a carefree life, living the easy life of someone with money, free time, and beautiful girls at his side. But the world was a dark place, and he had no choice but to gradually adapt to it. Drawing on the knowledge he had gained over two lifetimes, he rose step by step and painted a picture all his own.