A small mouth

He is characterized by calmness, frequent grumbling and complaining, and no important achievements are expected from him...

He is characterized by... 

being quiet,

 complaining a lot, 

and not expecting significant accomplishments due to his "narrow-mindedness." He usually has difficulty adapting to a new environment.

 

Also... 

* Generally kind-hearted 

* Friendly and has many friends 

* Often complains and grumbles, "cowardly" and rarely happy.