Erasmus made 13 changes to the starting line-up that lost to New Zealand at the weekend.
Schalk Brits will start as number eight and will lead the team onto the field.
Only left-wing, Makazole Mapimpi and centre, Lukhanyo Am, retained their positions in the starting 15 for the clash in Toyota.
Regular Bok captain, Siya Kolisi, will start on the bench.
Thomas du Toit, who arrived in Japan on Tuesday as an injury replacement for Trevor Nyakane, goes straight into the match on day 23 as a front row replacement.
3⃣ Boks have faced Namibia before
3⃣rd Test between SA and the “Biltong Boere”
3⃣ tries each by Schalk Burger and Juan Smith in 2007
— Springboks (@Springboks) September 25, 2019