Do I need a lawyer to file trademarks or patents in Japan?

In terms of patents, if you are eventually planning to file in more than just Japan, a PCT application might be something else to think about. A PCT application will grant you initial protection in up to 148 countries. However, you will need to eventually file for specific country/region protection no later than 30 months after the earliest filing date of your initial application.

For question 1, If you are a Japanese, or you have residence or office in Japan, then you could register trademark or patent in Japan without trademark attorney or patent attorney, otherwise you will need an attorney.
For question 2, I do not follow your question, but you should know that trademark is about brand name protection, while patent is about technology protection, there are different, namely a trademark could not be filed as patent, if your question is about this.

Hello

1. Though I don't practice Intellectual Property in Japan, I am not aware that an applicant must be a lawyer to be eligible to file patent or trademark in Japan. Japan Patent Office (JPO) will only require you to fill the necessary forms. If your patent or trademark application is revoked and you appeal up to the Intellectual Property High Court in Japan, then you will need to get a lawyer involved. Generally though, I always advise individuals and business owners to get IP lawyers involved when registering trademarks and patents because of lawyers' experience in this area.

2. I don't speak Japanese, but I think the 2 words 'Gyoseishoshi' and 'Shihoshoshi' because the last 2 syllables are the same, both words sound alike. I think the trademark office would be concerned about the similarity. The Office might find that it is not distinct enough. I advise you don't limit your searches to exact matches. It is important to capture names that are similar but not identical as is the case with the 2 names you have provided above. This is exactly how Nestle won a trademark infringement case against a small business over the use of the word 'A-Sashi' for a product. Nestle had registered 'Musashi'. The court gave the case to Nestle even though the two names are not identical but similar. Here's a link to the case http://www.smh.com.au/small-business/managing/musashi-v-asashi-nestle-wins-trademark-battle-against-aussie-small-business-20160106-gm0ffy.html

Good luck!

I am a Japanese patent attorney. I will answer you questions.
Q1. Do I need a lawyer in order to file a patent or trademark in Japan?
A1. If you can prepare the documents to be filed with Japan patent office in Japanese and in compliance with applicable regulations, it is legal to file patent or trademark application by yourself.
Q 2. Also, what is the difference between Gyoseishoshi and Shihoshoshi? Can they both file patents and trademarks?
A2. Gyoseishoshi cannot represent client for patent or trademark application in Japan. They are only limited to just prepare paperworks for immigration, incorporation, driver's license application and so forth. They cannot "represent" the client. They just prepare documents.
"Shihoshoshi" cannot represent client for patent or trademark application in Japan. They can represent client for recording incorporation and recording real property assignment, for the purpose of creating notice to third parties, thereby assuring safe possession and ownership of corporation and real property.
Benrishi, patent attorney, and Bengoshi, attorney at law, are the only agents who can represent clients to file trademark and patents in Japan.