Crypto-Christianity involves the secret adherence to Christianity while publicly professing another faith, typically arising during periods and in places where Christians face severe persecution or when their religion is outlawed. During the Roman Empire, many early Christians concealed their beliefs to avoid execution, a strategy distinct from those who chose martyrdom under Emperor Trajan's policies that demanded recantation or death. Centuries later, in Japan, Christianity was introduced by Saint Francis Xavier in 1550 but was outlawed by the Tokugawa bakufu in 1643, who viewed it as a threat to their authority. This prohibition led to the emergence of 'kakure kirishitan' or 'hidden Christians,' who secretly practiced their faith for over two centuries until the ban was lifted in 1858, leaving behind camouflaged religious artifacts as a testament to their enduring belief.