This is a badge for a medical foundation called the Doujin-kai. Dou 同 means 'same;' jin 人 means
'humanity.'
Kai 会, of course, means 'association.' You can see the first two kanji on the reverse of the
badge.

This group was established in June, Meiji 35 (1902). Abolished in Showa 20 (1945) at the end of the war.
Its express purpose was to develop medicine, health, and medical care in Asian countries, mostly China
and Korea. For example, they trained Chinese exchange students in hospitals and schools in Japan,
shipped out Japanese doctors to hospitals in China--most often as teachers--, and established medical
facilities along the rail lines in Korea. The doctors were shipped as far south as Bangkok and Singapore,
and by Taisho 1 (1912) 329 Japanese doctors had participated. However, at this point the range became
too wide, so after 1912 almost all the assistance went to China.

During the late 1930s and up to the end of the war, the group had its share of turbulence and topsi-
turviness.

There are obviously more interesting facts to relate, but one thing I did not find out was why these
badges were awarded. I suspect they were member badges. There are various colors on the badges.
The heart signifies a unity or humanity and the dragon may be symbolizing China.

(The information above is from the
40-Year History of the Doujin-kai)
Japanese Doujin Association
同人会
Case inscription reads 'Red Star Badge.'
Supporting Member Badge.