 If you liked 20th Century Boys |  ...then you might like Alive: Saishuu Shinkateki Shounen |
Friends...Comrades...Both manga are about a male who has to deal with something or someone trying to take over the world. In one story, it's about one of his childhood friends trying to brainwash everyone and in the other, it's about his friend who wants to make everyone disappear. Both are thrilling action/mysteries that are addictive and filled with serious topics and a moving plot.