Japan had been forcibly opened to trade by the US Navy a decade before the US Civil War, so in 1879 they were getting news like any other 19th century country - photographs, newspapers, and telegraphs. The Civil War had been over for 14 years at that point, but was still a major topic in US culture, so any Japanese fellow who wanted to find out about the details would find it fairly easy to do so.
Japan had been forcibly opened to trade by the US Navy a decade before the US Civil War, so in 1879 they were getting news like any other 19th century country - photographs, newspapers, and telegraphs. The Civil War had been over for 14 years at that point, but was still a major topic in US culture, so any Japanese fellow who wanted to find out about the details would find it fairly easy to do so.