Jo-Wilfried Tsonga got the job done against Laslo Djere in the second rubber, but that was preceded by Dusan Lajovic's 6-1, 3-6, 7-6 (7), 7-6 (5) upset of Lucas Pouille.
In Brussels, Belgium's David Goffin (ranked 12 in the world) will be out to embellish his phenomenal record in the competition against 185th ranked Australian John Millman.
Darcis, a Davis Cup hero in Belgium, clinched the victory with a 6-4 7-5 6-2 win over late replacement Jordan Thompson to put his side into November's final against France, who completed a 3-1 win over Serbia earlier on Sunday.
But there was no doubting his commitment to the cause in the Belgian capital on Friday as he sent down 34 aces in a come-from-behind 6-3 3-6 6-7 (7-5) 6-1 6-2 win that silenced a partisan home crowd.
France played their last final in 2014, losing in Lille to Roger Federer's Switzerland.
A huge net cord at break point down went the way of Kyrgios at the start of the decider and, perhaps sensing it was his day, the Australian showcased his talent - encapsulated with a double-handed backhand victor with both feet off the floor en route to a gutsy victory.
Neither of the Belgians play a great deal of doubles but with Peers' regular Davis Cup partner Sam Groth not in the team, the Aussies will field a new-look doubles team.
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Lleyton's Hewitt Australia are desperate for a first final since 2003, with volatile but talented Nick Kyrgios back in favor with the captain. France captain Yannick Noah was critical of his own performance.
Confidence restored, the 1.8m baseliner started to find his range with some crunching returns to level the match at 1-1.
Kyrgios, who was eliminated in the first round at Wimbledon but won a Masters 1000 series title in Cincinnati prior to his US Open disappointment, insists there is no comparison between him and Tomic, who admitted to feeling "bored" during his defeat to Mischa Zverev in straight sets at Wimbledon.
The tie concludes with the reverse singles on Sunday, when Kyrgios is scheduled to meet Goffin, followed by Millman up against Darcis. "I'll have to improve our communication for the next rubber". Mikhail Kukushkin had given the hosts the lead by seeing off Guido Pella 6-7 (5/7), 7-6 (7/5), 6-2, 6-4. Boris Becker, recently-installed as Germany's head of tennis, saw his team edge 2-1 ahead of Portugal in Lisbon.
In the play-offs, where the winning teams will compete in the World Group in 2018, Japan's tie with Brazil in Osaka was overshadowed by a racism row.
Switzerland, the 2014 champions, are 1-1 against Belarus while Colombia and Croatia and Hungary against Russian Federation also shared the opening day's honours.