Hi Marivo , it is a signature ......Kawasaki Nagamitsu
We are the Pilgrims , master, we shall go
Always a little further : it may be
Beyond that last blue mountain barred with snow
Across that angry or that glimmering sea...
The variation in signature is explained on the page I linked above.
The page shows two different styles of writing for "Nagamitsu."Since ancient times the signatures (mei) on the tangs (nakago) of Japanese swords have occasionally been carved by individuals other than the swordsmiths themselves. In some cases one swordsmith would carve the mei of another working with him. Sometimes a student would carve the mei of a sword made by the master swordsmith. At other times the master swordsmith would carve his name on an exceptional blade made by one of his students. These types of signatures are referred to as "dai mei" and "dai saku mei". During the Showa era (WW II period) it was a wide spread practice for a group of swordsmiths to have their mei carved by a single individual. Sometimes this was done by one of the swordsmiths in the group; other times it was a separate individual. When one individual carves the mei of several swordsmiths, such carved signatures are termed "nakirishi mei". This practice was particularly wide spread in the Seki area (Mino/Noshu region). Seki was the principle region for sword production during the Showa era. Below are several oshigata demonstrating this practice.
Thanks for the answers, there is not much know about this smith, only he's a showa smith??
All I can find out is his real name was 川崎專逸 Kawasaki Senitsu.