Both are feel-good, slice-of-life high school dramas that make you feel nostalgic with characters you love and want to root for and best friends who clearly like each other but won't admit it.
Both dramas are feel-good, slice-of-life college dramas. They both follow a group of friends as they enter their first year of college and looks at the struggles and joys that come with friendships, relationships, and college. The characters all seem real and complex.
In A Good Way is not a Korean drama (it's Taiwanese), not set in high school (it's set in college), and the focus isn't completely on the romance, but the same theme is at the heart of both dramas: friendships, relationships, and growing up. Both shows are set in the 90s and explore the lives of their characters as they transition to adulthood and go through all the trials and tribulations that come with that period of transitioning and figuring out friendships and relationships. They both portray relationships with incredible realism, fully develop all their characters into real, flawed, multidimensional people (no real antagonists here), and create these day to day slice-of-life portraits that are full of nostalgia and happiness.