Monster, ES: Eternal Sabbath Recommendations
Same type of assassin, a very psychologic story, characters trying to change their own lives.
The antagonists Johan and Isaac are VERY similar.
The psychology described in both manga is great and some what similar to each other.
Very similar in relation of how the assassins deal with people.... They both also have very psychological-filled plots.
These two are similar as they both have characters in search of someone who has committed crimes and are hard to catch. Both very good psychological mangas with interesting characters.