Seal cases and metal frames Founded in 1947

A well-designed seal case protects a seal from damage or loss, makes carrying and transporting a seal safe and easy, and is an elegant accessory.



July 1, 2022
The latest catalog is completed.
Koseido Case Catalog vol.2

New products and "Prime Series" are also posted.
December 16, 2021
Notice of new product sales
From December 22, 2021, two products, "Piano" and "New Ryukyu", will be on sale.
Please take a look at this opportunity.
January 16, 2021
New Prime Series launched
December 1, 2020
Upcoming Prime Series featured in the December edition of The Journal of All Stamping & Seals
more  buy
June 30, 2020
Utility model rights obtained for purse-shaped seal case
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Company Profile



I am the third-generation Representative Director of Koseido, which originated in 1947 as the Kasai Koseido Metal Frame Shop specializing in making metal-frame cases for the seal stamps that are commonly used in place of signatures in Japan. Prior to joining Koseido, after college I worked for two years in the manufacturing department of a food company where I gained invaluable experience in manufacturing technology and services. When I became Representative Director in 2016, I brought this experience to a company with a tradition of high-level craftsmanship and success . We at Koseido remain dedicated to our original commitment to craftsmanship that creates satisfied customers and gratified employees.

Eiki Kasai
Representative Director



1947年 Hiroki Kasai establishes Kasai Koseido Metal Frame Shop and begins manufacture of metal frames for seal cases in Nishijima, Minobu City, Minamikoma District, Yamanashi Prefecture
1976年 Sakae Kasai becomes head of the company and expands the variety of seal cases offerings
1980年 New factory constructed
1982年 Sakae Kasai incorporates the company as Koseido Ltd. and becomes Representative Director
2008年 Utility model rights obtained for a unique rounding process for metal frame hinges, increasing frame safety
2016年 Eiki Kasai becomes Representative Director
2020年 Utility model rights obtained for a purse-shaped seal case
2021年 Prime Series launched

Company Data

Company name Koseido Company Limited
Capital 5 million yen
Location Nishijima 1814-1 Minobu City, Minamikoma
District Yamanashi Prefecture 409-3301 Japan
Telephone 0556-42-2555
FAX 0556-42-2753
Bank The Yamanashi Chuo Bank, Ltd.
Business content Manufacture and sale of metal frames seal cases


Nishijima 1814 -1 Minobu City, Minamikoma District, Yamanashi Prefecture 409-3301 Japan