On October 5, 2014, fans on Reddit discovered a hidden a cappella verse on one of Donald Glover's websites. It was confirmed by Gambino that the verse syncs up with the instrumental portion of "V. 3005 (Beach Picnic Version)".
While STN MTN is free, the proceeds from the sales of Kauai are dedicated to maintaining and preserving Kauai island, which the second half of the EP is named after. The letters STN MTN are an abbreviation/disemvoweling of Glover's hometown, Stone Mountain, Georgia.
STN MTN is a concept mixtape where Glover is asleep dreaming he "ran Atlanta", with songs based on modern day southern hip hop. The mixtape ends with Glover awaking from this dream on the Hawaiian island, Kauai. Kauai is a concept EP. Unlike STN MTN, Kauai focuses on themes such as love, nostalgia and passion, using alternative R&B. A song from the EP Kauai, "Retro [Rough]", is based on Gambino's earlier song, "Love Is Crazy" featuring Eugene Cordero, from his mixtape Sick Boi.
STN MTN / Kauai has received generally positive reviews. DJ Booth gave the project a 4.7/5 stars, calling it "a cohesive project... it's Gambino so there will be at least some depth to make a follow up review worth while." Zach Dionne of Complex gave a positive review saying that "In a couple songs, he flies us there, thousands of miles away from Atlanta, to see for ourselves."
Kauai debuted at number 18 on the Billboard 200, selling 16,000 copies in its first week. In its second week, the EP rose to number 16 on the chart, selling 19,000 copies, bringing its two-week total to 35,000 copies. In its third week, the EP dropped down to number 46 on the chart, selling 7,000 copies, bringing the total album sales to 42,000 copies in the United States.