Yoko Tsuno: The Cannon of Koa — Roger LeLoup

Yoko, Vic and Pol are in Switzerland, testing a new civilian jet plane. At the end of their contract, they suddenly find out that they've unknowingly been preparing a mission for Japanese Intelligence. During World War Two, the Imperial Army had tested a colossal cannon, that was later thought destroyed – but massive calibre shells have now been delivered to an arms trafficker in a small Asian country. It's up to Yoko to locate the terrible weapon …