The Mysterious Aliens

Zorori and Ishishi have traveled to a far-off planet to rescue Noshishi. The space aliens that abducted him are using him to test out Earthling's intelligence. Since they have no more room on their planet, they want to take over the Earth but want to make sure they can do it easily. Noshishi fails the intelligence test, which is comprised of four riddles, but Zorori steps in to ace the test and save the Earth... Or has he? Looks like the test had a second part: A test of strength. Zorori now must face four fierce space monsters or he and the Earth are doomed. Based on book 11.