Hermanus was selected to represent Western Province at the premier South African rugby union competition for high schools, the Under-18 Craven Week, in 2012 in Port Elizabeth.
[5] After finishing high school, Hermanus joined the Western Province Rugby Institute in 2014.
He made eight starts for the side during the regular season of the competition – scoring two tries in their Round Eight match against the Blue Bulls U19[6] – to help them qualify for the semi-finals.
[8] In April 2015, he was included in a South African Under-20 squad to tour Argentina as final preparation prior to the 2015 World Rugby Under 20 Championship:[9] He scored a try in their 25–22 victory over Argentina in the first match[10] and played the full 80 minutes of the second match.
He didn't play in their semi-final match against England, which they lost 20–28 to be eliminated from the competition by England for the second year in succession,[16] but did come on as a replacement in their third-place play-off match against France, helping South Africa to a 31–18 win to secure third place in the competition.