The top two in the regular season both won their semi-finals in six matches and are expected to have a close series ahead of them. Getting off to a good start was key, and early on things were going Tappara's way, as Christian Heljanko was looking unbetable in goal before they broke the deadlock.
The first goal came with just over 14 minutes played, when the puck was dumped in behind the KooKoo net before Emil Sylvegard and Ondrej Pavel used their strength to win possession and set it back for Justin Addamo to finish.
But the advantage lasted less than a minute - Vilmos Gallo weaved his way through the defenders in the Tappara zone before striking home a wonderful equaliser to send the sides in level after one period.
The Kouvola side were still finding Heljanko tough to beat in the second period, but the match turned in KooKoo's favour at the midpoint, when Jimi Suomi cut in from the left, deked past the defenders and struck high above the goaltender for another superb individual goal.
Three more minutes were all KooKoo needed to open a two-goal lead, as Joonas Oden collected the puck at centre ice before playing it across for Marcus Davidsson to finish at close range.
With 10 minutes left in the match, KooKoo survived a second Tappara powerplay, only to concede soon after getting back to full strength when Joachim Blichfeld's centre was diverted into the net by Addamo.
The Battle Axe then went for broke in search of an equaliser, pulling Heljanko, only for Robert Rooba to chase a long clearance and cleverly knock the puck back for Otto Paajanen to tap into an empty net and secure KooKoo a 4-2 win.
KooKoo will host game two on 4th May, with Tappara coming to Kouvola in search of revenge.