Neither. It means that there were no other Samurai after him. As you now know, there are different meanings of the word "last".
Last week, I ate steak three times. Last week = the week before this one = the previous week.
The reigning king is called Stephen. The last king was called David. Last king = the king before this one = the previous king.
I have eaten my last apple. I have to go shopping. Last apple = the only apple remaining in my house
He was the last king of Scotland. Last king = after him, there were no more kings of Scotland.
Sometimes, words and phrases have more than one meaning. Context makes the meaning clear (to native speakers, at least).
I missed the last bus so I'll have to get the next one. (I missed the bus that was due to come before the one I'm now planning to catch.)
I missed the last bus so I'll have to walk home. (I missed the bus which was the last one of the day going where I wanted to go. There are no more buses on that route until tomorrow.)