I found them to be pretty detailed actually. I mean, of course it’s only tailored to what we need to know in order to understand the circumstances of the plot and the main characters, but since European history in the 16th century was pretty intertwined and convoluted, we need quite a bit Also sometimes they mention sea battles as well as famous seafarers and their achievements, which already sent me to Wikipedia more than once The central aspects of the historical detours seem to be catholicism and protestantism, mainly expressed in the lives of Elizabeth I. and Maria Stuart.
Regarding the pirate story, we finally see some action on various levels! And I must say, the author handles this pretty well, and writes in quite a funny/witty style at times.
E.g. I was wondering how he’d express difficulties in communication between people of different nationalities, and whether he’d gloss over that and just make them “magically” understand each other without it being clear which language they speak, but he solved that elegantly by using furigana to express what was actually said in the respective language (while the meaning was expressed via Japanese as expected). Of course this only lasted for a few sentences, and then this issue was settled and everything was expressed in Japanese.
What made me chuckle: 「吐きそ……」-「我慢しなくていいぞ」