Cognitive counseling is one of a method to improve the cognitive problem. This study is a case report for a 5th grade student who has difficulty with fraction and decimal. To solve his problem, we supported his learning by hypothetical instruction and lesson induction which was cognitive counseling methods. As a result, hypothetical instruction helped concept acquisition about fraction, and lesson induction promoted to reflect his calculation of decimal. Finally, he could assessment himself about his answer and explanation in the case, but could not reflect the assessment on the final exam. In the future, we should support his assessment between some mathematical problems and generalize the methods.