It could show a friendly relationship. Maybe they have become comrades after some adventures together. Ophis feels comfortable enough around Naruto to sit on his lap casually, like how good friends would have a relaxed and trusting interaction.
One possibility is that it's a comical situation. Naruto could be completely shocked and flustered by Ophis sitting on his lap. His friends might walk in on them and misunderstand the situation, leading to all kinds of humorous misunderstandings and banter. Or Ophis could be using Naruto as a convenient seat while observing something interesting in the ninja village, much to Naruto's embarrassment.
One possibility is that it could be a moment of great shock for Naruto. He might be initially flustered, his face turning red as he tries to figure out what's going on. Maybe Ophis is seeking comfort or has some ulterior motive in this rather intimate - for Naruto - position. He could stutter and try to ask her what she's doing.
He would probably feel embarrassment. Naruto is a bit of a blusher when it comes to unexpected physical contact, especially from a female. His cheeks would turn red and he would struggle to find words.
It might also just be a normal part of their relationship. If the fanfic is set in a world where they are very comfortable with each other, it could just be a casual display of their closeness without any major relationship shift, but still showing how important they are to each other.
A possible story could be that a young child had a bad day at school. When the child came home, the mom was sitting on the couch. The child ran to her and sat on her lap. The mom then gently stroked the child's hair and listened as the child told about the mean kids at school. She comforted the child with kind words and a warm hug, making the child feel better.
In some Western cultures, sitting on a friend's lap might be seen as a very casual and friendly gesture among close friends, especially in a jovial or party atmosphere. However, in more conservative cultures, it would be considered inappropriate as it violates the norms of personal space and propriety.
No, sitting on a son's lap in a family setting is not appropriate as it blurs the boundaries of a healthy parent - child relationship. It may also make the child uncomfortable or send the wrong message about personal space and appropriate physical contact.
Culturally, sitting on someone's lap can have different meanings. In Western cultures, for instance, it is not common for an adult or even a growing child to sit on someone else's lap outside of very young childhood. It is associated with a level of familiarity and closeness that is often restricted to specific family relationships like a small child on a caregiver's lap. In some Asian cultures, it may be more common within the family but still with certain age and relationship limitations. Overall, it reflects the cultural values regarding personal space, family relationships, and propriety.
One memorable long ride sitting on lap experience could be during a long road trip. I was a child and sat on my father's lap while he was driving on a scenic coastal route. I remember looking out the window at the beautiful ocean views and feeling safe and warm. He pointed out different things along the way like lighthouses and seagulls.