Muthusamy, a left-handed batsman who bowls left-arm orthodox, sent down five overs as India posted 202 without loss on a rain-curtailed day in Visakhapatnam at the start of the three-match series.
Durban-born Muthusamy, 25, is part of South Africa's new generation of cricketers eyeing a permanent spot after the retirements of Hashim Amla and Dale Steyn.
"It is really special. My forefathers are from south of India in Tamil Nadu," said Muthusamy.
"But I am firmly South African. I am quite a few generations down the line. Unfortunately I don't speak Tamil, I am a thoroughbred South African."
South Africa, led by Faf du Plessis, is in a rebuilding phase after what Muthusamy likened to a "change of guard".
But he said: "There is fresh energy in the room. And it is in our DNA, the South African fight that we are well known for and that's what we will keep doing."
The day belonged to India Rohit Sharma who smashed his first century, making 115 off 174 deliveries, in his new role as Test opener.
Sharma -- India's limited-overs star -- along with Mayank Sharma, who hit 84, pulverised the opposition bowling with their aggressive brand of cricket.
The opening pair together smashed 23 fours and seven sixes, but Muthusamy is still hopeful of a South African fightback on day two.
"Obviously a tough day in the office. Sharma and Agarwal batted really nicely, we have to put in the hard yards tomorrow and hopefully comeback stronger," said Muthusamy.
"There is a reason it is called Test cricket... it is not easy, it's tough. Some of the world's best players are playing in the opposition.
"I have just learnt from the first day, you got be competing every ball. Just hang in there, plug away."