Resin composition, molded article, master batch, and manufacturing methods therefor

A production method for a master batch, comprising:

• a step of melt-kneading
• an aggregate of a cellulose fiber (A),
• an amorphous resin (B) having a glass transition temperature of 160° C. or lower,
• a crystalline resin (C) having a melting point (melting peak temperature) of 80° C. to 150° C. and a melting start temperature lower than the melting point by 30° C. or more, and
• a defibering auxiliary (E) having a boiling point of 120° C. or lower;
• wherein:
• the amorphous polymer (B) is a polymer having an ester bond, an ether bond, a urea bond, a hydroxyl group, an amino group, or a carboxyl group;
• the crystallizable polymer (C) is an olefin-based polymer;
• and
• wherein:
• the amorphous resin (B) is present in an amount ranging from 5 parts by mass or more to 100 parts by mass or less based on 100 parts by mass of solid content of the aggregate of cellulose fiber (A);
• and
• the crystalline resin (C) is present in an amount ranging from 10 parts by mass or more to 150 parts by mass or less based on 100 parts by mass of solid content of the aggregate of cellulose fiber (A).