If the injury occurs in a Quidditch - related scenario, the other members of Ginny's Quidditch team could be main characters. They would feel responsible for her safety during the game. Neville Longbottom could also be a main character. He might offer his support to Ginny, perhaps using some of the plants he's learned about in Herbology to help with her recovery, and be a source of comfort during her difficult time.
Hermione could be a main character. She would use her vast knowledge of magic to try and find a cure or treatment for Ginny's injury. Luna Lovegood could also be important. She might have some unique insights or magical remedies that could help Ginny. And of course, Ginny's parents, Arthur and Molly Weasley, would be main characters. They would be extremely worried and do everything in their power to take care of their daughter.
There could be the tattoo artist. He or she might be an interesting character with a lot of stories about the tattoos they've done in the past. They could have a unique personality and play an important role in guiding Ginny through the process.
Obviously, Ginny is one of the main characters. Since the title is about her getting 'the talk'.
Ginny herself is the central figure. There might also be a character who represents a glimmer of hope for Ginny, like an abolitionist who secretly tries to free the slaves. Even if they don't succeed immediately, they are an important character in the story as they give Ginny some sense of possibility for a different future.
Perhaps Ginny gets injured in a fight against some dark wizards. Her family and friends are distraught and they all try to contribute in her recovery. Some might use magic to heal her physical wounds while others try to keep her spirits up. Or, she could get injured during a magical experiment gone wrong in Hogwarts. Her classmates then come together to figure out how to reverse the effects of the accident that caused her injury.
Maybe it's a group of rogue Death Eaters who are still loyal to Voldemort's ideals. They believe that by kidnapping Ginny, they can disrupt the peace in the wizarding world and send a message to those who defeated Voldemort.
Obviously Ginny would be one of the main characters since she's the one who faints and is pregnant. Harry could also be a main character as he might be her partner or husband, and he would be involved in the story, supporting Ginny through the pregnancy.
It could be a long - time boyfriend that we haven't known much about in the original story. Maybe he's a character who was in the background but now becomes central to the plot.
Obviously Naruto would be a main character. Since he has the kyuubi sealed within him, any change in the kyuubi's state would directly affect him. He would be in the center of the story, trying to deal with the kyuubi getting bigger.
Shinichi is a given as the main character with the flu. But his detective friends, like Heiji, could be important characters too. Heiji might come to visit Shinichi and end up getting involved in a mini - mystery that is somehow related to Shinichi's flu situation, like someone trying to steal a medicine that could cure Shinichi.
Joho is the main one for sure. But there could also be a love interest. Maybe someone who has always had feelings for Joho and uses this time when he's sick to get closer to him and show their care.