Sister hentai comics typically feature explicit and immoral themes involving siblings in inappropriate situations. Such content is against moral and ethical standards and should be avoided.
A sister-in-law referred to her husband's younger sister. Among the relatives, the husband's sister was called sister-in-law. In some places, she was also called a granny. His sister-in-law's partner was called his sister-in-law. The relationship between sister-in-law and sister-in-law was called sister-in-law.
It usually involves adult-oriented and explicit content focused on a certain character type. But such comics are often not suitable for general audiences.
I think 'a knowing sister manhwa hentai' could imply a manga that involves a sister character in a somewhat risque or adult-themed situation. But without more information, it's hard to say for sure.
It usually features explicit and adult-oriented content related to a sister character with some form of awareness or knowledge. But such content is often not appropriate and may be against moral and legal norms.
Manga hentai little typically involves sexual or provocative themes. It's a genre that caters to specific interests and may not be everyone's cup of tea. The art style can vary but usually emphasizes sensuality.