¾«¶«Ó°Òµ

The Sakuragaoka Laboratory continued to create a string of hits starting with its 1938 launch of Japan's first commercial vitamin E product Juvela, which was developed from wheat germ oil extract. Juvela was closely followed by other successes such as the sanitary tampon Sampon and La Vende, a medicated talcum powder. At this point, the Sakuragaoka Laboratory research team had swelled to 74 members and outgrown its Tokyo facility. To expand further, Toyoji purchased the Tsurumaki Silk Mill just north of Tokyo in Honjo, Saitama, and on December 6, 1941, established Nihon ¾«¶«Ó°Òµ.—Eisai's second incarnation—with ¥180,000 in capital. In just two days, the Pacific War would begin. Toyoji was 53 years old.

In May 1942, the Japanese government issued a public declaration under its wartime national policy, enforcing industrial adjustments aimed at streamlining Japanese industry. Under the legislation, all companies with ¥500,000 or less in capital were to be either consolidated or closed down. Accordingly, Sakuragaoka Laboratory Co., Ltd. and Nihon ¾«¶«Ó°Òµ. were merged together on December 26, 1944, with the new company retaining the name of the latter—Nihon ¾«¶«Ó°Òµ.

In the first half of 1951, after overcoming Japan's chaotic postwar years, the company finally turned its first profit since establishment. Furthermore, Nihon ¾«¶«Ó°Òµalso developed what would become the first in its hit Chocola vitamin series, which would sustain the company for many years to come—Chocola A. The vitamin A product was used to treat a wide range of symptoms, including night blindness, dry skin disorders, and malnutrition in children. On the heels of strong, extended Chocola A sales, Nihon ¾«¶«Ó°Òµfollowed up its success with the launch of additional vitamin C and D products as well, respectively, Chocola C and Chocola D.

In 1953, Nihon ¾«¶«Ó°Òµenjoyed rapid growth through the launch of several new products, including the anti-asthmatic Asthphyllin and gastric ulcer treatment Methaphyllin. Two years later, in May 1955, a decision was made at a general shareholders' meeting to change the company name from “Nihon ¾«¶«Ó°Òµ.” displayed in Chinese characters to “¾«¶«Ó°Òµ.” in simpler, katakana script. Two of the reasons for this change were that a shorter, easier-to-write name would be more readily remembered and more efficiently written. Nihon ¾«¶«Ó°Òµhad begun as a manufacturer of products for the wartime military. Eisai, however, was able to survive the postwar chaos and help welcome in Japan's coming period of strong economic growth under a new company name through shifting its focus in response to the huge changes taking place in the country at the time.