Sorry for my english, first of all.
Summe up:
The story was Initial called Ragnarok, but suffer an alteration to "Sword of the Dark Ones". If you are looking for a nice battle manga with a very decent and short background story, and some body exposure, blood, love , revange, hate, you will have it.

Story: 8
Leroy is the main character, this world takes place in a world dominated by "Dark Ones". These monsters devour anything within their pass, and are incredibly strong. Leroy's exemplar type of mercenary, that catch's attention of some sort of underworld guild and plus, a strange girl called Lena shows up offering him a peculiar job related to that guild and so that's how the story starts to develop.
The story might seem simple at first, but as more in to it as you keep advancing. It's a very short series, I read it online, latter on I felt the urge to buy it due the its awesomeness.

Art: 9
A very refined art, for the time it was made. Details can be a strong point of this manga, along with some textures and a nice work with black inking tone(s). Characters are well appealing, and mysterious as you get to know their past and experiences.

Characters 8
Honestly, I like them all, specially the small girl. Things are not what they seem like at first. But if I tell you examples here, I would be ruin the fun of it!
But you can trust me, its very impressive, even for a sword who can talk and materialize.

Enjoyment / Overall: 9 or 10
I vibe a lot with how simple and fast story like this could leave such satisfaction and hunger for more. Every chapter gets more and more interesting, and the fact you can see things "uncensored" makes it even more of an enjoyment!
Specially I enjoyed a lot every chapter, page, tones... everything!

PS: I would love to see an anime OVA of this series someday.