Although the plot is different from Age of Youth, a lot of the ideas are similar. In both shows, 5-6 adults are roommates where cry together, laugh together, fight together, etc. A prominent idea in both, is the process of their adulthood. The characters struggle with finding jobs, balancing their relationships, and so on.
They also share some of the same cast! Son Seung-won is one of the main characters in Eulachacha Waikiki and is a side character in Age of Youth. Shin Hyun-soo makes a brief appearance in Eulachacha Waikiki and is a side character in Age of Youth.