The symbol is a unalome, a representation of the journey to reach enlightenment. The path starts in the centre of the spiral, and as you continue up or down this path you are wandering, becoming more conscious of your surroundings.
"Parts of Japan gave criminals tattoos on their arms. Many are simple lines around the arm. On the bottom line, the third left, I can see the sign of “悪”, bad in Japanese. This was Kishu´s (紀州/now Mie and Wakayama prefecture) tattoo.