The Ryuo’s Work is Never Done!(2015)

Ryuuou no Oshigoto!

The Ryuo’s Work is Never Done! is a story about a teenage boy named Yaichi Kuzuryu who happens to be the strongest shogi player in history, holding the top title of “Ryuo”(Dragon King).
One fateful day, shogi-loving elementary student, Ai Hinatsuru, appears before him claiming that he promised to be her master. But was such a promise really ever made? Thus began their master and disciple relationship!

(Source: Bookwalker Global)