Jeong-ho and David are part of Penny, Maggie, and Nina's circle of friends. They've created their own app and are going to travel to Silicon Valley to pitch it to an investor. While they may have impressive coding abilities, they're not very perceptive and sometimes miss crucial details.
Jeong-ho finds pineapple on pizza to be a dealbreaker in a relationship and even dumped a hot boyfriend over it. He's more outgoing and confident than David, who's more nervous. After identifying as gay for several years, David has recently come out as bisexual, which wasn't well received by some of his other friends.
Their first appearance was in Penny and the Silver Key #3, which shows an outcome of their efforts. The 2 are aboard a SpaceX rocket on its way to Mars with some powerful Silicon Valley people, and have to wear modified shock collars that explode if they lose control of their emotions or go against their masters. The dwindling resources have forced the passengers to resort to cannibalism, but so far Jeong-ho and David are on the winning team.