he did not kill them yet.
An aventure should be aware of his surroundings all the time, he may be sneaking upon them with his weapon only to show them how easly they could be killed by a someone else.
next chapter he may touch her with the blade and say - if i were an enemy you would be dead now-
If you guys want spoilers, you can read the ln/wn (not sure which) at novelupdates. Just go to this manga page on mangadex and click the novelupdates link.