It turns out that the virus he has created is only a bluff and that the Book of Prophecy is just only a Death Note in disguised.
The laughing gas is the virus that Friend plans to unleash to the world.
Friend was trying to protect the Earth from a real alien invasion
He was only evil because there was a bigger threat on the horizon, like Scorpius
, or one of those other Well Intentioned Extremists
Maybe his death by the hands of Blackwatch is fake, and plans on recreate his virus at Japan so that he can unleash it there
If you think he is going to Germany, think again. He is leaving to Japan and plans on causing destruction as a masked villain. Why? He lost Sara to Gackto
After leaving the hospital, Johan figures he'll go start up some shit in Tenma's home country, Japan. There he meets Fukubei
, from whom he takes the "Book of Prophesy" from and decides to start up the Cult of Friendship. When the going got tough, Johan picked Fukubei
to be the scapegoat and the corpse for his official "death"
. In addition, Fukubei
is not Kanna's father — Johan is, which also explains why Kanna shares a physical resemblance to Johan's sister, Anna, and is apparently the only Urasawa character to be affected by Mukokuseki
Given their goal, his working for them would make perfect sense.