These are words from the most famous Japanese song outside Japan, thanks to Gilbert & Sullivan using it in The Mikado. ‘Mr. Mitford’, W.S. Gilbert reminisced years later,

Mitford was a good musician, once being described as perhaps the finest amateur cornet player of his day. He successfully passed on both the words and tune to Gilbert and Sullivan; where the words are different from the original, this was surely deliberate. The first line of the original is ‘Miya-san, Miya-san’, which would translate as something like ‘Mr. Prince, Mr. Prince’. One of the charms of the song is that the writer is innocent and unworldly as well as being a bit tongue in cheek. But Mitford took princes seriously and replaced ‘san’ with the more respectful ‘sama’, which fits the tune just as well.

The question that Gilbert and Sullivan left in the air in The Mikado is answered in the second verse:

The purpose of the song was to rally forces against the ‘enemies of the Emperor’. But who in Japan would be an enemy to a fifteen-year-old hidden away in Kyoto with no power whatever?

Mitford was bored. He was stuck in Edo ‘vegetating as usual after a trip [to Japan's west coast] and clearing up the accumulation of rubbishy papers which a long absence generates’. There was no shortage of things going on – machinations were raging in Kyoto and Osaka for the future of Japan – but unfortunately Mitford did not know about them and had to rely on unreliable rumours.