Kunimoto lost his original opponent, Hyun Gyu Lim, who moved into the main event vs. Tarec Saffiedine after an injury to Jake Ellenberger.
The event is set for January 4 from Singapore and will mark the first time the promotion has visited the country.
Dutra is 11-2 and was the top choice on The Ultimate Fighter: Brazil. However, a torn ligament in his hand ended his tournament run.
Kunimoto is 15-5-2 and also making his UFC debut.