Although Ryotaro Imamura acted fast, that didn't mean he acted on impulse without thinking. Player of his stature couldn't allow such amateurish mistakes afterall unless he was in some short of predicament.
However right now, he was as calm as still water. And most of all, he was very much aware of Hiro's capabilities.
Thus before leaving his position, he had already called for the reinforcement from other defenders who were closed to him.
And the reason why Ryotaro Imamura was called the adhesive of the Sagan Tosu U-18 team was very much because of such reasons.
As the term adhesive referred, he was like adhesive which held the formation of his team together. And whenever he acted, he always acted while taking the position of his teammates into consideration.