Rave, Psyren Recommendations
both protagonists go on a dangerous adventure to bring down some external dark force that threatens the fate of the world.
Shounen, Adventure, Action, Mystery, Romance (light).
Both are comparatively "shorter" shounen series with strong links between so-called "arcs", to the extent that every arc moves the story closer to its (satisfactory) ending.
Note: This is actually a huge accomplishment for a shounen.
Main protagonist teams up with other people and tries to save the world.