The task facing KTP was a mammoth one, given their heavy defeat in the first leg away from home on Thursday, and any chance of a comeback tonight was all but ended within three minutes when Onni Helen scored his second of the tie to put TPS Turku 4-0 up on aggregate.
That's how things stayed until early in the second half, when Rangel's goal finally had the Kotka side on the board, but seven minutes later the four-goal lead was restored by Albijon Muzaci from the penalty spot.
Nathaniel Tahmbi made it 2-2 on the night with a little over a quarter of an hour to play, but KTP weren't even able to salvage some pride, as a second penalty for TPS six minutes from time, converted by Aapo Bostrom, ensured the second-tier side won 3-2, winning both legs of the tie.
TPS are back in the top flight for the first time since 2020, while KTP's three-year stay in the division comes to an end.
At the top of the table, TPS' neighbours Inter Turku regained first place but failed to take full advantage against an HJK side who are no longer in the title race, as the pair drew 1-1 in Helsinki.
Bart Straalman put the visitors ahead midway through the first half, but it took HJK less than 10 minutes to draw level through Alex Ring.
That's how things stayed, meaning FC Inter go ahead of KuPS but only on goal difference, having played a game more. HJK end their three-match losing run, but they are still without a league win since the Championship Group began.
Only one point separates the top three after Ilves secured a first win in four by beating 10-man Gnistan 3-1 away on Saturday.
Roope Riski missed a penalty 20 minutes in, but when Ilves got another chance from the spot five minutes later, Jardell Kanga made no mistake.
Oliver Pettersson levelled matters early in the second half, but Riski made up for his earlier failings by restoring the lead three minutes later. In added time, Rachide Gnanou received a straight red card, and Ilves took advantage, wrapping up the win three minutes later through Marius Soderback.