User blog comment:Valeth/Rider of Imperial Capital/@comment-4802891-20190727043520/@comment-4802891-20190731011702

I've made research in the meantime, and still can't find direct relevance to the flag. By pure conjecture and guesses I arrived at the conclusion that said flag is the national flag of Japan back then and "Advance" becaue planting it somewhere indicates "Japan" has reached another point farther outside their mainland?