Denied a number of tries in relatively short succession, a penalty gave them the extra points to lead 12-3. Another high tackle by Buller gave HK a further three points to go 15-3 ahead in the 69th minute, but then the Buller boys were back in the HK half and two tries later took the lead 15-17.
It was then play-on for a further five minutes. Buller charged down a late attempted drop goal thinking they had the game in the bag but then the miracle. An off side call and HK were awarded the penalty for first five James So'oialo to kick HK into the Meads Cup final by one point.
HK Coach Chris Wilton was visibly emotional after the game, feeling "numb and humble" as it sunk in that he had helped lead the first HK team to a Meads Cup final.
He admitted he had gone into a "dark place" in those last few minutes.
"There was a lot of tension... the game is never over until the end... it was pretty epic."
He said the missed opportunity to score the extra three points was not mentioned at half time.
"It was done and dusted, it was onwards and upwards. We knew a 13-point cushion in the second half wasn't going to be enough. Buller always finish strongly.
"We were able to play a territory game putting a lot of pressure on Buller but we weren't able to capitalise off that. We spent a lot of time in their 22 without scoring. It was bit of a concern."
He said they were relying on defence but had let the gaps show, especially for the first Buller try.
"We need to be more accurate on attack, and we'll be working on those gaps to make sure they're not there this Saturday."
Horowhenua Kapiti now face five-times defending champions Wanganui who beat South Canterbury 24-29 in their semifinal.
Horowhenua Kapiti Rugby Football Union chief executive Corey Kennett said to win a Meads Cup semifinal for the first time and to have the final at home is a great result for all the hard work and effort by the team, coaches and managers.
He said one of the mantras the boys use is 'stay connected'.
"The boys are winning games because they are staying connected with each other and now they're feeling connected with the local community.
"We need the community this Saturday more than ever. We need them there and we need them to help our boys to win the Meads Cup."