Two questions?

1. In South Korea, if Han men want to marry Korean women, they need to abide by relevant laws and regulations, including legal residence permits and other requirements. Generally speaking, if you meet the requirements, you can get a legal residence permit or work in Korea.

2. If Han men and Korean women get married and have children, then the children can apply for F4 entry card. F4 entry card is a permanent residence visa, and the holder can freely enter and leave Korea without applying for a visa again. However, obtaining F4 entry card needs to meet certain conditions and requirements, including age, minimum income and Korean language ability. You can consult relevant departments and lawyers for details.

According to your description, even if this 24-year-old boy has a Korean stepmother, if he wants to get an F4 entry card, he needs to meet certain conditions and regulations.