Otladisa only made his PSL debut in October last year, ironically against Sundowns, after impressing Stars coach Roger de Sa with his performances in the MultiChoice Diski Challenge.
However, the 21-year-old has caught Downs' eye, having scored once with a fine solo effort against Baroka at Peter Mokaba Stadium in November in eight league appearances for Dikwena.
Otladisa is currently nursing an injury and may only link up with Pitso Mosimane's side next season according to De Sa, who will shortly lose left-back Siyabonga Zulu to the Brazilians.
Otladisa is relishing linking up with the 2016 African champions.
"The feeling is something else because we all know Mamelodi Sundowns is the best team in South Africa and one-time African champions," Otladisa tells KickOff.com.
"So it is a dream come true to have signed for them now. The next step now is to take my game to the next level, winning trophies, breaking records and that is what is going through my mind right now.
"But, before everything else I have to say this, that I'm taken aback because this is happening in just a short space of time. So obviously I'm going to be in some kind of shock."
Otladisa fractured his fibula on December 27 on the club's first day of training after the festive break. He is hopeful he can make his return at the end of next month.
"The injury is coming all right and they [the doctors] said I'll be back at the end of February. I'll be actually be playing at that time," he reveals.
"The shin bone, it's only fractured, it was not broken. Sadly it just happened at training when we got back from the recess in December on our first day back at training.
"With little professional football experience, this injury has taught me to learn the game better, that these things happen. And for me it'll not really put me on the back foot."