The Japanese language characters as tattoo designs are called Kanji tattoos. These characters, unlike in the English language do not represent a single letter of the alphabet but rather, they represent whole objects and complete ideas. They are pictographic characters, some of which have more than 30 different strokes in them! It is easy to express complex thoughts with just a few characters in these languages.
The written Japanese language has of two types of written characters in use today. They are the Kana and the Kanji characters. Kanji is the name given to those characters that have evolved from written Chinese. In fact, all of written Japanese is said to have evolved from the Chinese language, but over the years they have also come to develop some characters of their own to accommodate those sounds unique to their spoken language.
Since most of the characters are similar in these two languages, one shouldn’t assume that they also mean the same. Many characters mean the same, however there are usually pronounced differently in these languages. Many characters although they look the same, can mean completely different things in the two languages. And of course there are those characters that are unique to the Japanese.
Given the complexity of these languages and their similarity, it is easy for one (not fluent in those languages) to get them mixed up or wrong. So, if you’re planning on getting a Kanji tattoo it’ll do you good to find a tattoo artist who is fluent in the language, and who is also able to understand you well. Very often kanji tattoos end up not meaning what the wearer thinks it does! If you are a native English speaker, remember that it is quite difficult to literally translate English expressions into Kanji. What sounds very good in English may make no sense at all when translated to Kanji.
There have also been instances when the characters were split into meaningless halves, written in reverse like in a mirror image, written with some strokes missing (again becoming meaningless or meaning something else) or mistakenly joined to form a single character which can be thoroughly absurd in the Japanese language. Make sure you do your research well before you have the characters inked permanently.