One possible theme could be self - discovery. Dealing with her period might make Sakura more in touch with her body and her femininity, leading to new understandings about herself.
I'm sorry, I haven't come across specific 'sakura on her period fanfiction' myself. You could try searching on some popular fanfiction websites like Archive of Our Own or FanFiction.net.
One possible plot could be Sakura initially being embarrassed and not knowing how to handle it. Her friends, like Ino and Hinata, notice her discomfort and come to her support. They help her understand what's happening and give her practical advice on dealing with the physical and emotional aspects of getting her period.
The fanfiction could explore Sakura's character development by having her face new challenges related to her period. She may have to learn how to balance her normal life, her duties as a Cardcaptor, and the physical and emotional changes she's experiencing. This would force her to adapt and grow, like learning to be more assertive in asking for help when she needs it. Also, it could make her more empathetic towards other girls or women she encounters in her magical adventures.
I think Hinata would be a great supporting character. Hinata is very empathetic and kind. She would be there to listen to Sakura's concerns and offer her quiet support. Also, Kakashi could play an interesting role. He might not fully understand what's going on but still offer his general wisdom and support to Sakura in his own unique, laid - back way.
A plot could revolve around Sakura's discovery of new ways to manage her period while in a world full of magic or special powers. For example, she might find a magical herb that eases the cramps. Along the way, she could share this knowledge with other female characters, creating a story about female empowerment and health awareness.
One possible plot could be Sakura Haruno trying to still carry on with her ninja duties while on her period. She might struggle a bit with the physical discomfort but still show her determination and strength. For example, she could be on a mission and have to hide her condition from her teammates to avoid being seen as weak.
One possible storyline could be Sakura still trying to carry out her Cardcaptor duties while dealing with the discomfort and mood swings of her period. For example, she might struggle a bit more during battles or have moments of self - doubt. Another could be her friends noticing a change in her behavior and trying to be extra supportive without fully knowing the reason at first.
One popular sakura period fanfiction might be those that focus on characters having picnics under the sakura trees. The beauty of the sakura blossoms creates a romantic backdrop for the story.
One unique way is to have Sakura's period be linked to a special power she has. Maybe the hormonal changes during her period enhance her abilities in a certain way, but she has to learn to control it. This would add an interesting twist to the typical period narrative.