The key to reading manhwas is to immerse yourself in the story. Pay attention to the details in the art and the expressions of the characters. You could also join online communities or forums to discuss and get different perspectives on the manhwas you're reading.
One main cause is lack of sleep. When you don't get enough rest, your blood vessels under the eyes can become more visible, creating the appearance of dark circles. Another factor could be genetics. Some people are just more prone to having darker pigmentation around their eyes. Also, allergies can play a role. Constant rubbing of itchy eyes due to allergies can lead to inflammation and dark circles.
You can try some adult-oriented comic websites. But be aware that accessing such content may have legal and ethical considerations depending on your region.
Some popular platforms to read manhwas are Lezhin Comics and Tapas. Both offer various genres and stories to choose from. Also, you might find some on Naver Webtoon, which has a large user base and a diverse range of titles.
You might find manhwas on apps specifically designed for comic lovers. Check out apps like Tappytoon. Also, some libraries might have digital collections of manhwas that you can access with a membership.
Websites like Lezhin Comics and Tapas often have a good collection of manhwas. You could also check out manga apps on your mobile device. Just search for manhwa reading apps in your app store.