Kashima, who will take a 2-0 lead into the return leg at the Azadi Stadium, will first have to play Kashiwa Reysol in the J League on Tuesday, meaning the Persepolis tie on Saturday will be their fourth match in 11 days, having played Cerezo Osaka on October 31.
"The players may be physically and mentally tired now but after a couple of days of rest, they will be looking forward to the return leg," Oiwa said.
"We know how supportive the Persepolis fans are but we have a great chance to win the AFC Champions League for the first time and my players will overcome their mental and physical fatigue and be ready for the return leg," he added.
Kashima will have to be for Persepolis are unbeaten at home in the AFC Champions League this season, having also overcome first leg deficits in the Round of 16 and quarter-finals to advance.
"We know that we will be playing in a stadium filled to the brim in the return leg but I don't believe my players will be intimidated simply because we are focused on winning the AFC Champions League," said Oiwa.