I read this manga a year ago and can barely remember details about it, but I know that the main character meets an almost-dead slime. He helps it and it grows into a big slime with muscles.
Later, the main character builds a spire in a desert and it explodes. Also, a demon child (I think) wants to learn from the main character and then later, there's this bear that took over as a mayor or something and is bested by main character then turned small.
Also, a game developer/assistant is following the main character then dropped some papers, then a muscular bunny picks them up (I think again). Thanks for the help.