Tantei Kibukawa Ryousuke Jikentan 'Tasogare wa Ruri no Tsuioku'

The familiar members of the Kibukawa Detective Agency take on a murder case involving the past of a female therapist renowned for her regressive hypnotherapy.

Masao Ikurumi visits a clinic for an interview, where a key witness in a murder case is to be regressionally hypnotized.
The witness, who had been missing for three years and was found with a head injury 10 days earlier, says he has no memory of the incident or the time before.

The female therapist who performs the regression hypnosis seems to know the witness...?
What secrets are hidden between the two?