An assistant to the high school counseling teacher, Rinne Akegami is an introvert who only understands what is true. As if from a revelation from God, she can point out the culprit of any crime there. What complicated matters, however, is that not even she herself understands how she does this! This is where Touya Iroha comes in — he deduces "her deductions" in order to reveal the truth, once and for all!