Pachinko File
If you are interested in the actual game and its role in Japanese society, the paper published in International Gambling Studies is a primary scholarly source.
If you are researching the novel Pachinko , the paper offers a deep dive into the immigrant experience. Pachinko
It uses cultural identity theories (such as those by Stuart Hall and Homi Bhabha) to explain how the characters navigate their "foreigner" status in Japan. If you are interested in the actual game