Here is a cafe that I like to frequent. The coffee is good and there is free wifi. They also make their own desserts. The waffles and brunch are a tad overpriced, but you can get a great homemade muffin and Americano for about 6,000 won.
Daniel Gray is a Korean-American Adoptee that returned to Korea in 2005 to rediscover his roots. He is a Korean food expert that has appeared on Bizarre Foods, Parts Unknown with Anthony Bourdain and more. He is the president of Delectable Travels and owns two restaurants: Brew 3.14 and Brew 3.15 in Seoul.