Greetings! I have a few pointers to make on the misconceptions about a Christian using a sword and why it is relevant to today...
Also going to cover what it means to be a Christian Samurai, and the path I walk as one.
Let's start with the meaning of a Christian Samurai:
1) The kanji for samurai is very simple (侍
if you want to get technical, it means to serve. As Christians we are called to serve God as we live our lives and walk alongside him, a Samurai is one who serves his master. He/she follows the master who commands him/her to serve unwaveringly. If you look at the concepts, we are servants to God as Christians and we are called to follow unwaveringly and walk alongside Him. These mean the same.
2) As a Christian Samurai myself, my life belongs to no other but God and Jesus. Back in history, many samurai denied their lives were for the master they served when the Daimyo commanded them to commit seppuku or ritual suicide. Instead, they stated that their lives did not belong to the daimyo, but to The Lord, and refused. Many were martyrs and died for that faith. I am not afraid of death in my body because I have eternal life with Jesus.
3) A Christian Samurai is also one who serves his or her people to know Christ. We are called to make disciples in many lands and give the love of God to all. We all have spiritual gifts The Lord has given us, and we should join together in bringing love through those gifts. This means we should also love those who don't love and need it.
For using a sword in martial arts as a Christian:
1) I was taught at a very young age, when I started Iaido (Japanese swordsmanship) by my cousin saying to me that "the sword isn't merely wielded by the hand, but by the heart. If your Heart is for God, and it is full of love, your blade will be after God as well, but if your heart is full of hate, your blade will be evil, and those who don't understand this are unfit to use a blade." A Christian Samurai doesn't use his sword to murder but to protect. I believe God will not judge you if you kill someone in the process of protecting yourself or others, if your heart is for God. Of course, we should fight as a last resort and try to win with the sword in the sheath if possible. A common mistake of society is that as Christians we cannot and are not allowed to kill under any circumstance, but this is not true. There is a verse in Matthew (I think? Unsure exactly) that tells us Jesus told his disciples to sell their coats and buy two swords. Meaning that Jesus was all for self-defense on his mission to save all of us. At the same time, when Peter cut a man's ear off in the garden the night Jesus was betrayed, and Jesus healed the man, He rebuked Peter. This means that Peter was trying to stop God's master plan, even so with intentions of protecting Jesus. However, Christ calls us to use a spiritual sword, the Bible as our guide, and use The Word as our sword and use it in love, coming back to the sword being wielded by the heart. 2) we are called to love our enemies. This is never going to be easy, especially if using a sword, but it comes back to what the intent is. Love means many things and if it means to protect yourself for God's plan for you, it is not wrong.
I am a Christian Samurai and I fight a spiritual battle the world will never see unless they choose The Lord. All things I do, I do in love after God's heart.
If anyone has questions or comments feel free! Amen and God bless you all!