The establishment of today’s Hayashi, Doi & Associates dates back to 1992 when Tsunenori Hayashi established Hayashi & Associates, which subsequently merged with Doi’s firm in 1996.

Although not huge in scale, the Firm is characterized by the following attributes. First, we handle an almost equal ratio of domestic and overseas applications, with patent attorneys and office staff on hand to offer comprehensive assistance with patent, trademark, and design applications. Moreover, although medium-sized, we have many patent attorneys and maintain an efficient operational structure upheld by the various management systems and the utilization of IT.

Furthermore, through the provision of a rational performance assessment system that our staff can relate to, the Firm aspires to provide a workplace that is capable of accommodating a range of lifestyles and allows our staff to adopt a healthy work-life balance.

In recent years, the intellectual property industry has undergone significant change. We strive to cope flexibly with this change and our staff members continue to work hard in contributing to clients through the provision of our IP services.

Finally, I would like to introduce our philosophies:

  1. We will strive to make high-level contributions to clients and society through the provision of IP services, and work hard to earn respect by demonstrating dependability.

  2. All our staff will make continuous efforts to achieve personal growth through their work in IP, and the Firm will work to foster an open culture characterized by mutual development through healthy competition.

Kenji Doi
Patent Attorney and Representative Partner


1992 Tsunenori Hayashi established Hayashi & Associates
1995 Kenji Doi established Doi & Associates
1996 The two firms merged to form Hayashi, Doi & Associates
2004 Sendai office was established
2010 Yokohama office was established



Head Office

BENEX S-3 Bldg.,
3-20-8 Shin-yokohama, Kohoku-ku, Yokohama-shi, 222-0033 Japan



Sendai Office

2-10-2, Murasakiyama, Izumi-ku, Sendai-shi, 981-3203 Japan




Yokohama Office

5-1-7-102 Kounandai, Kounan-ku, Yokohama-shi, 234-0054 Japan




  1. Domestic and overseas patent applications
  2. Applications for utility model registration
  3. Applications for trademark registration
  4. Applications for design registration
  5. Representation in specific infringement case
  6. Representation in suit for canceling a trial decision
  7. Appraisals
  8. Invention incubation
  9. Prior art search
  10. Representation for applying a standard essential patent


  • 11 Patent Attorneys
  • 3 Patent Engineers
  • 6 Paralegals
  • 1 General Administrative Staff