Where did you get your coin?
Your coin is definitely not genuine. If it were, it has the characters for year 8, putting it in the 1870s.
Your coin has very grainy surfaces, indicating it is from cast metal. This is a low tech way of counterfeiting.
None of the genuine coins would have the extra ONE you circled. This is an indication that whoever made the coin was not very familiar with it. In the USA we see fake coins with similar errors like wrong text, wrong year, wrong image, etc. I assume they are all made in China by people unfamiliar with how the original coins should look.
There are other methods for detecting fakes like measuring the weight, checking for magnetism, but in your case the coin is easily spotted as fake without these additional tests.
A genuine one yen coin would be worth $30-50 or more. Your fake is probably worth $0.50 or less.
Sorry for the bad news but

to CCF.