This national flag of Japan is known as the Nisshohki or Hinomaru which means sun disc in Japanese.
This WWII era Japanese flags was given to a Japanese soldier by his family, relatives and neighbors. Their signatures and words of encouragement are addressed to this Japanese soldier and written on this flag.
During the WWII era or more specifically, the date of this flag, the people of Japan, the military and the Japanese nation belonged to the Emperor who was known as Ten-noh in Japanese. Therefore, many of the messages written on this flag includes phrases pertaining to the loyalty to the Nation or Emperor. This loyalty was thought of as one of the symbols of courage or bravery.
From what has been translated, I have learned that the owner of this flag lived at Inaho-machi, Otaru-shi in Hokkaido, Japan. Hokkaido is Japan's second largest island and the largest, northernmost of its 47 prefectural-level subdivisions.
It is thought that a women by the name of Kikuno was the flag owners fiancee back then. The flag owner is thought to have been born in the year of the Tiger, possibly 1914 or 1926.