The sword that kills, and in the saying it belongs to, the killing is not a villain's: the seven characters 殺人刀活人剣, the sword that kills, the sword that gives life, are one Zen master's two hands, what he takes from a student and what he gives, and a master must have both. In the sword schools the killing sword is the stroke that strikes first and ends the other's answer; on a wall it has been read as the sword that takes life beside the sword that preserves it, and as the ruler's sword that kills one evil so that ten thousand may live. A person who chooses this half alone may mean any of those, and which is yours. The text here writes 殺人剣 with 剣, the word as the modern dictionaries head it; the Zen books mostly write the killing half 殺人刀, with 刀, the single-edged blade, and an Edo story of the swordsman Tsukahara Bokuden writes it with 剣, as this text does. 殺人 is killing a person, which is not the same as murder.
Its other half, Life Giving Sword (katsujinken), is offered on its own.
殺人剣 is composed of the kanji 殺人 (read satsujin) meaning "killing a person" and 剣 Sword (ken).
Note that the Japanese word satsujin is often translated as murder but this is not strictly correct as satsujin only means "kill a person" which includes murder but it also may mean killing someone evil or killing someone in defense of oneself, one's family or one's country - so it does not have the strictly negative meaning that the word "murder" has.
We want you to be as happy with the meaning as you are with Master Takase's art. To learn more, visit Philology of 殺人剣.