There's 'Citrus' as well. It's about two step - sisters who gradually develop unexpected feelings for one another. It has a lot of cute moments where their relationship deepens, and the art style if it was made into a visual work would also be very appealing.
Sure. 'Bloom into You' is a popular yuri fanfic. It tells a story about two girls exploring their feelings for each other in a very tender and realistic way. The character development is great, and the relationship between the two main characters is both sweet and complex.
Another one is 'Adachi and Shimamura'. It focuses on the slow - burn relationship between the two girls. They start from a rather ordinary acquaintance and slowly grow closer, with many small, cute interactions along the way that are really endearing.