Ye Tianchen seemed to have agreed to protect the people of Dragon Country as they headed to M country to exchange secret documents. This wasn't considered an accepted mission, nor was there any mission binding Ye Tianchen; he was merely intrigued upon hearing Cang Lang mention that M country had a Superpower Special Agent Team with many experts, which sparked his interest and enthusiasm.
Having been reborn in this life, if he didn't go overseas to meet those experts and show them what for, they would really think Dragon Country was easy to bully. Today they come borrowing money and grain, tomorrow they might want to seize islands and lands—truly, too despicable.