Doraemon: There is a classmate named Sheng Nai

When he woke up, Chi Chen found that he had traveled to the world of Doraemon, and was bound to a system called Professional Savior. After being told by the system that he must complete the task of saving the world before he can go back, Chi Chen reluctantly embarked on the road of saving the world. I thought that as long as I followed the protagonist group and paddled the water to touch the fish, I would be able to complete the task easily. Until... why do I have a pistol in my house? Why...