I guess they don't mean literally an 8 year old, because the typical 8 year old's emotional control/capacity doesn't really match the expectation of "man without fear"
I checked out the live drama but 🤔 the actors for the manager and the "lottery-kun" are actors I really disliked in the Kyou Kara Ore Wa live drama so I dropped it. the first five minutes were pretty funny though.