The 31-year-old is the cup top scorer with seven goals, including six from their giantkilling victories over Villarreal, Racing Santander and Espanyol, and his third-tier club are on the brink of a possible final meeting with either Barcelona or Valencia.
Infante scored and set up their dramatic injury-time winner to knock out Espanyol in the quarter-finals last week, and was carried off the pitch on the shoulders of ecstatic fans.
A few hours later, he was opening the doors to his bank at 8am with television cameras waiting to greet him.
Infante has become the unlikely hero of Mirandes's fairy-tale cup run, which has been all the more impressive as they have beaten top-flight sides over two legs three times.
The fact Infante has to dash back from the away legs in his car overnight to be back in time for his day job has caught the imagination of the country.
"I'm here seven hours a day, 8am until 3pm. It's in the afternoon when I immerse myself in my other job," Infante told regional newspaper Deia.
"This media attention is down to the work of everyone at the club. I've perhaps received the most attention, but I take it the same as everything else, calmly.
"I understand this is a business, that when things go well you are on a real high, but when they go badly you are criticised and brought back down to earth."
Tuesday's first leg is in the small industrial town of Miranda de Ebro, population 40,000, where the club operating on a budget of 1.2 million euros is in the last four for the first time to take on the 23-times winners Bilbao, who have an annual budget of around 60 million.
ONE PERCENT CHANCE
Bilbao are sixth in La Liga, boast two Spanish World Cup winners in Fernando Llorente and Javi Martinez, and are coached by Argentine Marcelo Bielsa.
"We know they are favourites," Infante added. "I would say it is a 99 percent chance for them to win and one percent for us, but we have hope and enthusiasm and won't give it up easily."
The second semi sees Barcelona visit Valencia on Wednesday, with Pep Guardiola's side suffering an injury crisis and, judging by their last two outings, a dip in form by their own high standards.
On Saturday, they were held to a 0-0 draw at Villarreal to slip seven points behind leaders Real Madrid, who they knocked out in the quarter-finals last week.
The Spanish and European champions, last year's losing finalists, head to the Mestalla with David Villa and Andres Iniesta ruled out, and Pedro and Alexis Sanchez doubts.
Valencia are nine points behind Barca in La Liga in third place and also drew on the weekend, conceding a late equaliser for a 2-2 draw at Racing Santander.
