Well, for something similar to 'Sstudy', 'Fullmetal Alchemist' could be a good choice. Both often have deep emotional undertones and rich world-building. However, they still have their distinct differences in plot and character development.
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.
You might find 'Naruto' comparable to 'Sstudy'. They both have elements of adventure, friendship, and personal growth. But keep in mind that the art styles and specific plot points can vary significantly.
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.
Well, 'My Hero Academia' could be similar. They share elements of adventure, diverse characters, and a focus on personal development and facing challenges.
You could check out 'Tokyo Ghoul'. Both have a darker atmosphere and explore themes of humanity and the supernatural. The character development and storylines have some parallels to Darkfall.
You might find 'Fullmetal Alchemist' somewhat similar. Both have deep storylines and explore themes of morality and human nature. Also, the art styles have certain similarities in their detailed and immersive depictions.
I think 'Berserk' could be similar. It has a dark and intense style, and complex themes like violence and fate.