Jamie Joseph revealed Japan spent three years plotting their stunning 19-12 dismantling of Ireland in Shizuoka.
The Brave Blossoms boss hailed one of the World Cup's greatest ever upsets by insisting it was a triumphant gameplan painstakingly distilled and refined.
Japan's Kiwi boss claimed Ireland, in contrast, had only been working on this match for one week and paid the price.
Former Highlanders boss Joseph insisted Ireland had not disrespected Japan, but was adamant that disparity in preparation had proved pivotal.
"There was a lot of relief around what we were able to do," said Joseph.
"We have been preparing for this game for a hell of a lot longer than the Irish have.
"We've been focusing on today for the last year at least, and probably subconsciously the last three years.
"And Ireland have been thinking about it since Monday. So we just felt we had to execute our plan."
Asked if Ireland's limited direct preparation to face Japan showed a lack of respect, Joseph replied: "Not at all, they are a great rugby team, they played last week and have had a shorter turnaround.
"They've played a lot of Test matches recently, they are professional athletes.
"Our preparation window for the World Cup has been a little different, we've been training a hell of a lot."
Japan set their home World Cup alight by dumping Ireland on their backsides in serious style at the Shizuoka Stadium Ecopa.
Joseph's men blitzed Ireland in all areas, recovering from a 12-3 deficit to storm to a victory that left the raucous home crowd in raptures.
This was a triumph every inch as impressive as Japan's last-gasp 34-32 victory over South Africa in Brighton at the last World Cup in 2015.
Wing Kenki Fukuoka sealed the result, haring into the left corner to leave Ireland outgunned and outplayed, with early tries for Garry Ringrose and Rob Kearney mere footnotes on the scoring charts.
Hooker Shota Horie led from the front in an all-court performance for the hosts, leaving Joseph purring at his continually developing game.
"He's a quality rugby player and this year he's been in great form," said Joseph.
"Physically, set-piece, it's something that wasn't high on his priority list.
"He was renowned for his skill-set but now he can do both loose work and tight.
"He can throw out the back passes, he can jackal like a flanker but he can also scrummage powerfully and put in little kicks and things like that.
"I think he's the ultimate tight forward, and he's a big reason why we performed tonight."
Ireland boss Schmidt was left to praise the winners and admit his side must now tend their sizeable wounds.
"I'd like to first of all congratulate the Japanese team for the energy, the intensity, the skill they brought to the game tonight," said Schmidt.
"They are a big team, they played big and they were very difficult to contain.
"I felt we probably controlled the first quarter reasonably well, to go 12-3 up with two tries scored.
"It's probably exactly what we'd asked for, but the longer the game went the more oxygen they got from penalties and from the skill that they showed and you've got to commend them for that. It's not the first time we've seen them do it, it's not a surprise to us that they were incredibly tough to beat.
"The quality even of Michael Leitch coming off the bench – I thought he really added value.
"Yu Tamura and (Timothy) Lafaele, I thought they got a bit of an armchair ride. We got penalised for a few offsides and then we became hesitant.
"Once we became hesitant we couldn't really put the same pressure on them as they were putting on us – and they got a real roll on."
