Luke Herden made the difference.
His powerful display in the midfield helped Southern to an impressive win at Bishopscourt.
His strong tackling shut down Kaikorai's attempts to break out, his powerhouse running with the ball in hand tested the defence and his long punting relieved pressure when Kaikorai was in the attacking zone.
Herden gave Southern the early advantage when he burst through the centre after six minutes and gave speedy wing Greg Zampach the space to run in the first try.
Southern looked in complete control when it led 10-0 after 19 minutes.
But a spirited Kaikorai team refused to concede and its counter-attacking play brought it back into the game.
Halfback Tomasi Palu sped down the short side from a scrum after 30 minutes and first five-eighth Cam Rutherford scored the try.
The scores were level at 10-10 at the break and Kaikorai was still in touch when it trailed by six points, 21-15, midway through the second spell.
The constant Southern pressure told in the last 15 minutes when it added two more tries.
Herden initiated the first with a strong burst and the try was scored by loose forward Sam Compton who added spark when he came on in the second spell.
Flanker Sam Gavigan was Southern's best lineout jumper with five clean takes while openside flanker Carl Anderson and lock Uili Kolo'ofai both had strong games.
The best Kaikorai forwards were lock Chris Brun and lively No 8 Jamie Williams.
Southern 33 (Sam Compton 2, Luke Herden, Greg Zampach tries; Hancock 2 conversions, 3 penalty goals), Kaikorai 15 (Craig Baird, Cam Rutherford tries; Rutherford conversion, penalty goal).
Halftime: 10-10.
Referee: Liam Scanlon.
