I can speak to South Korea a bit. There's basically a few things to consider about South Korean food culture:

1 - there's a phenomenally low female participation in the work-force (at least among OECD countries), which translates to a wife or mother doing most of the cooking at home. This is changing slowly, but still a dominant fact-of-life for most Koreans. So the default idea of a meal is "home cooking". Korean house-wives still maintain a broad set of cooking skills and can produce huge varieties of menus, often of healthy and filling meals. Soups of various kinds are among the most common type of meal, served with rice and sometimes noodles.

2 - for various historic, geographic, and cultural reasons, Koreans share of proteins has been lower than say, an American or European might expect in their diets. The bulk is made up of fresh and pickled vegetables, and rice as the main starch. Proteins are heavily sourced from the sea and come in a huge variety of critters, and are often supplemented or replaced with some kind of tofu. Of course Koreans eat beef, chicken, pork and so on. But it tends to be more expensive and less ubiquitous. You'll find some kind of sea creature in nearly everything you eat unless you're eating Buddhist temple food (which is also delicious and vegetarian). This is also changing, and as a result Koreans are getting taller and heavier. But there's a small cultural bias against very meat heavy meals and many South Koreans will describe the typical American-style meal as "greasy".

3 - somewhat paradoxically, restaurants are ubiquitous. In Seoul, you might find a dozen or more restaurants within an easy walk of where you live. They come in huge varieties, are often very narrowly focused in menu and offering, are intensely competitive, and are often not terribly expensive. Importantly, they frequently try to provide a "home-cooked" meal replacement and the kitchens will often be run by older women with not much more training than the average house-wife and will produce food that has similar flavor and nutritional characteristics. In market areas, you can find traditional styled soups with rice and unlimited basic side dishes (kimchi, etc.) for $5-7 and walk way stuffed.

4 - there is of course lots of street food in Seoul, but it tends to sit near very busy business districts or in markets. More importantly, there's a very big class of foods and restaurants that cater to "food you eat while you drink alcohol" and that tends to be fried, salty, meat or starch heavy, spicy, greasy and generally fairly unhealthy. It's also increasingly common to eat when not drinking and includes foods like fried chicken, instant noodles and so on. These are often upped with cheese and other such high-calorie add-ons. Most Koreans recognize this is trash food intended to be eaten while getting trashed, but to be honest, it's about as good for you as the average American diet is.

All that being said, the average Korean eats a much healthier diet than the average American. Most Koreans will have a well developed sense of taste for veggies and seafood and this starts very young. Here's a video of 30 days of school lunches https://youtu.be/0Kq_d0TUKS4