You could try 'Fantasy Expedition'. Both have elements of epic quests and a focus on character growth and exploration, and the art styles have some similarities in their detail and color usage.
I'd recommend 'Quest World'. It has a similar fantasy-driven plot and the style of drawing is somewhat similar to 'Quest Supremecy', with bold lines and vivid depictions of magical settings.
One manga that could be similar is 'Final Fantasy' as it often features fantasy worlds and adventure quests like Dragon Quest.
The plot of 'Quest Supremecy' manhwa mainly focuses on the protagonist's journey to overcome various obstacles and rivals to achieve supremacy. It's filled with adventure, mystery, and unexpected twists.
One manga that could be similar is 'Watchmen'. It shares elements of dark themes and complex characters like Batman.
One manga that might be similar is 'Parasyte'. It has elements of horror and action, like Gantz, and explores themes of survival and humanity's response to strange threats.
I think 'Fruits Basket' could be similar. It has a similar emotional depth and character-driven storylines like 'Swan'.
I think 'Love Hina' might be somewhat similar. It has elements of romance and character development like in Sextudy.
I think 'School Days' could be somewhat similar. It has similar elements of complex relationships and emotional turmoil.
Well, 'Parasyte' could be a manga similar to Kaijii. Both have elements of horror and mystery, and the character development is quite engaging in both.
It's hard to say exactly. But you might want to check out manga like 'Attack on Titan' as it shares some similarities in terms of intense storylines and complex characters.
Well, 'My Hero Academia' could be similar. They share elements of adventure, diverse characters, and a focus on personal development and facing challenges.