This manga is hard to get into, in that the main character is really difficult to sympathize with or get invested into. His basic premise of an assassin that doesn't actually want to kill works and as far as that went it was a reasonably strong story. But from there, he somehow becomes the head of the organization that kidnapped him in the first place, who were first portrayed as the villains, but they suddenly become the side the reader is supposed to be on the side of, with no justification given for why the reader should suddenly sympathize with them over any of their opponents. This is compounded by the fact that Freeman, as well as most of his companions, have very little character. The protagonist being a blank slate can work if the people surrounding them have strong characters that push them along, but here that wasn't the case. Rather, he's a character completely lacking personality and with no clear motivations or goals beyond the immediate situation he's in, but still the one pushing the plot somehow most of the time. This combined with the fact that there isn't really much of an overarching narrative, results in a story that doesn't really have much substance at all and is essentially pointless. The manga does have its strong points though, in that while Freeman may not have much of a character that's interesting or easy to sympathize with, the way he handles situations is interesting and pretty cool. What I mean by that is that while it really doesn't matter why he's doing any of what he's doing or who he is at all really, the actions he takes that make up each of the individual stories that make up the larger story are all pretty interesting. He dealt with opponents in ways that often had him being clearly overpowered, but in the end still looked pretty cool and were pretty varied, with strong action and a good sense of style, and that in a way can hold up the manga reasonably. The art was strange, in that it clearly had a lot of effort put into it, but it looked pretty bad to me with the shots that were supposedly meant to be eye catchers often being the worst of the lot, but it was something I got used to eventually. 

tl;dr: A manga that's lacking substance overall but has a decent amount of good moments.