There was much anticipation surrounding Teemu Pukki's return to his nation's domestic league for the first time since 2011, but it was his strike partner Santeri Hostikka who dominated the early proceedings for HJK.
He grabbed the opening goal of the league season after four minutes with a cushioned volley as the home side failed to deal with a long throw into their box.
Ten minutes later, Hostikka was afforded too much space on the left wing before cutting inside and firing into the top corner.
Ilves were back in the game in the 38th minute when Lauri Ala-Myllymaki's 20-yard drive went in off the post.
But the match turned when 16-year-old Otto Tiitinen came on with a quarter of the match to play for his Veikkausliiga debut.
Within a minute, he Maradona-turned his way into the box and saw his shot deflect off two HJK players before nestling in the back of the net, with Hostikka getting the final touch and going from hero to villain for the visitors.
Less than 10 minutes later, Tiitinen carved out another shooting chance and this time did not need the help of deflections to win the game 3-2 on the biggest day of his young career.
Liiga Cup winners Inter Turku continued their fine form this spring with a 1-1 draw at home to reigning champions KuPS.
After a goalless first half, the team from Kuopio broke the deadlock through Samuli Miettinen, but inside the final 15 minutes, Inter found a way through and equalised courtesy of Axel Kouame.
That goal meant the home side are now seven without defeat in competitive games since beginning their Liiga Cup campaign with a loss to HJK.
The surprise early pacesetters, however, are Jaro, who won 2-0 away at Mariehamn on their return to top-flight football after almost a decade away.
Jaro took little time adapting to the higher level, scoring in just the sixth minute when Kerfala Cissoko bundled the ball home.
Ten minutes into the second half, the Guinean was at it again with another close-range finish to double the advantage, with both goals set up by Albin Bjorkskog.
Top of the scoring charts is Mads Borchers, who scored a second-half hat-trick in VPS' dramatic 4-3 win over AC Oulu.
Niklas Jokelainen put Oulu in control with two goals in the first half, but a penalty from Borchers and a goal for Maissa Fall - assisted by Borchers - levelled the score with 20 minutes to play.
Borchers then put VPS in front, only for Oulu to hit back in the 90th minute through new man Marokhy Ndione.
But Borchers was not done there - a minute later, he was in the right place at the right time to force the ball home at full stretch and finally seal the win for the Vaasa side.
There were plenty of goals in Valkeakoski, too, where the home side Haka beat Gnistan 3-2.
There could have been more had both sides not missed penalties, but crucially for Haka, Simon Lindholm made amends and put them 2-1 up in the second half, having missed the chance to put them 2-0 up from the spot inside half an hour.
Then, when Tim Vayrynen missed a 90th-minute penalty to level the scores at 2-2, Haka went straight down the other end, and Jean-Pierre Da Sylva made it 3-1 to settle the tie before Gnistan added a late consolation.
Finally, there was disappointment for the other newly-promoted side, KTP, as they lost 1-0 at home on their return, conceding a 73rd-minute goal to Momodou Bojang of SJK.