This book was written by James Duncan Lawerence in 1979, I had read "The Mystery of the Chinese Junk" (1960) written by the same author in the same series and I didn't notice any racism back then, but when I started reading "Mystery of the Samurai Sword" I noticed it's filled with racist remarks and outdated language. The outdated language makes sense as it was written decades ago, but parents need to be aware of the language change. I started to write down each instance of racism, outdated language, and slurs but gave up after 31 pages. Notably, every asian character but one are just described as "the Ori*ntal" or "The Japanese", reduced from full characters down to their race.
Second complaint, for the first half of the book, everyone's weight is mentioned. Their hair, eyes, and clothing apparently aren't necessary for you to know, but their waistline is very important. Nancy Drew books, which are also penned by the Stratemeyer Syndicate, are full of eating disorder language, but usually Hardy Boys books are spared. Not so this time.
Third complaint, the Hardy Boys call up a man they've never spoken to before and do not ID themselves. They then ask if they can visit the man, and he says something along the lines of (I can't find the page again), "anything for the Hardy Boys." They didn't have caller ID yet, not that the Hardy Boys would even be in his contacts, and the boys didn't say who they were, but yet he knew. It's a small plot hole but one that I've seen before from the Stratemayer Syndicate.
Lastly, the characters are very dumb, particularly Joe. A man goes missing and a photographer had been taking photos earlier and Frank says the photos might be useful but Joe doesnt understand how, and has to explain to Joe in small words that the photos could contain evidence. This happens multiple times with Joe in this book and at the end Sam Radley, who works with the boys' PI father, asks why two of the criminals were involved with the crime and Frank has to explain to him that they were going to get a cut of the money. I think the issue here is that we can't hear the characters' thoughts, and so everything needs to be explained "out loud." I definitely feel that James could have accomplished this without making private detectives so dumb they forgot how photos work.
The story could have been interesting, but these issues really took focus.
Tw: Moderate racism and mild racial slurs.