Easy

• Buy them from Audible Japan or Audiobook.jp
  • [Audible (オーディブル)：本は、聴こう。｜ボイスブック・オーディオブック配信・サービス｜Audible.co.jp] goo.gl/1G7oKE
  • [忙しいあなたも、耳は意外とヒマしてる – audiobook.jp] audiobook.jp/
    • BTW, I strongly recommend audiobook.jp over Audible if only because Audible Japan is still maturing as a service. Audible is just growing pains galore and many dumb, byzantine rules — like that you have to not only have Japanese plastic (dumb, but fair enough) but remove all overseas plastic, expired or otherwise, from your Amazon Japan account (playa, what?). Literally, I kid you not, they seem more interested in their rules than in making money; it’s almost like dealing with a comically intricate government bureaucracy; like, I still buy books there, but do so shibushibu (grudgingly and almost under duress lol).
• Search for “ラジオドラマ” (radio drama, radio plays) on YouTube: [ラジオドラマ – YouTube] goo.gl/PhhjPs