I really like 'Sanegiyuu: The Unspoken Understanding'. It delves deep into the unspoken connection between Sanemi and Giyuu. The author does an amazing job of portraying their internal struggles and how they gradually come to understand each other better. There are some really touching moments in this fanfic that make it a must - read for sanegiyuu fans.
Social media platforms like Tumblr can also be a good source. There are many fans who post about their favorite sanegiyuu fanfics on there. You can search for relevant tags such as #sanegiyuu #fanfic and explore the posts to find some good reads.