We investigate the origin of the most iron-poor stars including SMSS J031300.36-670839.3 with [ { Fe } / { H } ] < -7.52 .
We compute the change of surface metallicity of stars with the accretion of interstellar matter ( ISM ) after their birth using the chemical evolution model within the framework of the hierarchical galaxy formation .
The predicted metallicity distribution function agrees very well with that observed from extremely metal-poor stars .
In particular , the lowest metallicity tail is well reproduced by the Population III stars whose surfaces are polluted with metals through ISM accretion .
This suggests that the origin of iron group elements is explained by ISM accretion for the stars with [ { Fe } / { H } ] \lesssim - 5 .
The present results give new insights into the nature of the most metal-poor stars and the search for Population III stars with pristine abundances .