There are several types of experts (qualifications) related to laws in Japan.
Links to english Wikipedia
Each of them are professionals in particular area. However, only “Bengoshi” (Attorney at Law) is legally allowed to represent clients for legal disputes and advocate at the district courts, family courts and more advanced stages of litigation.
If you need legal support in Japan, and if you need negotiation or litigation (lawsuit), it is advisable to consult a Bengoshi lawyer (attorney at law).