The theme is the famous "Duel at Genryu-jima" or Duel at Ganryu Island. To many martial artists, Miyamoto Musashi is known as the "sword saint" and certainly one of the most famous swordsman in Japanese history. To businessmen and armchair strategists, he is accredited as the author of the "Book of five rings" which has been translated to many different languages. His life has been made to TV series, movies, manga (Japanese comic books). Of course the most famous depiction of Musashi in movie was done by the late great Toshiro Mifune known as "Samurai Trilogy".
More about Miyamoto Musashi, the tales has been told countless time, and this is where fiction and real life got mixed up. By all account, Musashi's father is also an accomplished swordsman, but he showed no love to the boy. Musashi was raised by his uncle instead and by some accounts, it is likely that Musashi taught himself fencing. His first duel was at age 13 and from that point, he traveled around Japan sharpening his skills by defeating masters after masters and warriors after warriors. His fighting style is non conventional, he will often use whatever he can to win: arriving late to irritate his opponents, using high ground to his advantages etc. It was only matter of time he was destine to meet... Kochiro Sasaki.
Sasaki by general account, is a better swordsman techniques-wise. He is known for using a "nodaichi" or a long sword of 90cm long (typical katana blade is about 70cm long). Despite this large weapon, he is feared for his unusually fast and precise cut. His most feared technique is the "Reverse Swallow cut", by modern account it is done with a very quick down stroke followed by a very quick up stroke (much like swallow's tail changing direction in mid fight). Like they said, there can be no two #1... so these two met at Ganryu Island for a final show down.
The Duel:
Since by most account Sasaki is a better swordsman, Musashi must find a way to win by cunning. By this time Saksaki already has a lot of students, and if Musashi wins the fight, Sasaki's students for certain will take revenge, so he must be able to escape from the island quickly. He also must find a way to counter the 90cm long sword, and he must somehow unnerve his opponent. To accomplish this, Musashi was 3 hours late to the duel. He came by boat when the tide was favorable. Instead of using his 70cm sword, he reworked an old oar and made it longer than 90cm. By arriving late, he greatly angered Sasaki. At this time, Saksaki drawn his long sward and threw away the scabard. Seeing this Musashi further irritated Sasaki by commenting this as a bad omen as the sword will never meet the scabard again. Blinded by rage, Sasaki made the mistake of not noticing now Musashi has his back against the sea with setting sun also in his back. By the time Saksaki noticed his own mistake, it was too late. Musashi quickly leaped into air with sun in his back to deliver his downward blow with is long oar. Blinded by the sun and the reflections from the sea, Sasaki managed to make a cut. Sasaki's long sword actually was faster and was able to cut down Musashi's headband, but before he can complete his famous "reverse swallow cut", the long oar of Musashi was able to struck down on Sasaki's skull hence ending the duel. While all the spectators and Sasaki's students were still in shock, Musashi had already jump into his boat, and by this time the tie had truned again in his favor and sailed him away from the island.
While Musashi was a brash young man during his duel days, he spent his later life living like a hermit writing books and by all account, also a accomplished painter and calligrapher.
Here is the pen:

Here is Musashi in the air delivering the blow. Notice the setting sun behind him and the extra long oar in his hands

Here we have Sasaki holding an extra long sword

Pen uncapped

Hope you enjoyed the pen and a bit of history.
Kevin