My first time seeing a penis was when I was a child and my baby brother was being bathed. I was young and didn't really understand what it was. I just thought it was something different about him compared to me. As I grew older and learned more about human differences, I realized the significance of that physical difference.
I was quite shocked at first. It was something I had only seen in textbooks in a very clinical way before. There was a sense of curiosity mixed with a bit of embarrassment. I quickly looked away as it was not something I was used to seeing in person.
I was a bit shocked at first. It was so unexpected and it made me realize a new aspect of male sexuality. But then I also felt a strange sense of closeness, like we had shared a very private moment.
If a mom discovers inappropriate behavior between siblings like this, she would likely be shocked and immediately take steps to stop it. She would need to have serious conversations with them about appropriate boundaries.
If it was something a bit strange but not harmful, like suddenly making a really loud noise, I would probably be startled at first. Then I might laugh it off and ask him what on earth he was doing. I think in such situations, it's important to keep an open mind and not overreact.
The masters would probably be very confused at first. They are used to summoning heroic spirits with a certain set of characteristics and Naruto's appearance and abilities would be completely foreign to them. For example, Shirou might be shocked and immediately on guard, trying to figure out if Naruto is a threat or an ally.
In Naruto future reaction fanfiction, characters might react to various things. For example, they could react to new jutsu developed in the future. They might be amazed at the power and creativity behind it. Maybe Naruto himself would be excited to see how the next generation has advanced the art of ninjutsu.
Family members can provide practical help. For example, they can help with making doctor's appointments or taking care of daily chores. Emotionally, they should be positive and reassuring, telling the person that they will get through this together.