They have a complex and somewhat ambiguous relationship. It's not straightforward love but a deep connection based on mutual understanding and shared experiences.
In a Giyuu x Shinobu fanfic, the setting and plot can vary widely. Some might be set during the main events of the Demon Slayer universe, with them facing demons together. Others could be more of an alternate universe story, where they meet under different circumstances, like in a modern - day high school AU. The fanfic could also delve into their backstories and how those experiences shape their relationship. For instance, Shinobu's past with her sister could play a role in how she opens up to Giyuu, and vice versa for Giyuu's own traumas.
I would recommend 'Whispers of the Heart' for Giyuu x Shinobu fans. This fanfic focuses on their unspoken understanding. It's full of small moments that build up their relationship, like when Shinobu leaves a small flower on Giyuu's doorstep as a sign of her care. Also, 'Shadows and Sunlight' is worth checking out. It has a great plot that involves them having to go on a secret mission together and how that journey changes their relationship from colleagues to something more intimate.
Au999.9 was pure gold, and the gold content was no less than 999.9%. It was the highest value in the naming of jewelry. It was dark yellow in color and extremely pure. It shone with golden light and was bright. The markings were usually printed with words such as "Thousand Gold,""999 Gold," or "G999."
Tanjiro and Giyuu have a sort of mentor-student relationship. Giyuu offers guidance and support to Tanjiro on his journey, and Tanjiro learns valuable lessons from him. They also develop a sense of camaraderie as they face the challenges of the demon world together.