Why does my iPhone speak certain emoji in a Japanese accent?
It's possible you have a non-English language selected in Speech settings?


  Choose a voice for Speak Screen and Speak Selection
  
  Go to Settings > General > Accessibility > Speech. Enable Speak
  Selection or Speak Screen, or both. Select Voices. Choose the one
  voice and dialect you would like both Speak Screen and Speak Selection
  to use.


Ref: https://support.apple.com/en-ca/HT202362