Their voices often sound very familiar, and they don’t sound like AI—normally sound like they mean what they say, especially the deep-voiced man who sounds like he really gets into character. There are four or five usual voices and they pop up a LOT. Who are they?
We don't publish the information about those who do the recordings on renshuu, but they are indeed all native speakers, and there are a few that provide the majority of the audio (especially the two voices for the sentences).