It's a pretty good story about going into another world and the mc became a skeleton in a dungeon. what mystical adventures will he have.

What would happen if a person was selected to become the system's merchant.

Seventeen-year-old Kimura is your average, everyday otaku. However, his life of pulling all-nighters, sleeping in class and gaming is suddenly turned upside down when, in an attempt to save a kid from a car crash, he dies himself. Whilst his life flashes through his eyes, Kimura was given a chance to relive his life. He awoke moments later to find himself reincarnated into a body of a teen in a new unknown fantasy world!
But as if the nightmare couldn't have gotten worse. Whilst everyone was blessed with godlike powers, learning magic and battling techniques, Kimura was stuck with a levelling system, stats worse than of a farmer and one simple Synergist type skill- "Transmutation". 
Plunged into world where the strong trample over the weak, Kimura tries to survive striving to live his life to its fullest. Will he pull through in this dangerous world of monsters and demons with only his survival instincts and wits?

Amadeus Rye cannot remember his past. He cannot remember if he had a job or a family. All he knows is that he was reincarnated in another world... As the weakest monster. It's going to be a tough life...