I'd suggest checking manga forums or dedicated Bleach fan sites. They often have detailed breakdowns and recommendations on where to pick up after a specific part. Sometimes, the author or official sources might provide cues as well.
An interesting plot is crucial. It could be a story that takes place during a time not shown in the original manga or anime, like her early days as a captain. Or it could be an alternate universe story where she has different circumstances. Maybe she has to face a new threat that tests her in ways not seen before in the official story.
A good one often has a deep understanding of Unohana's character. It should capture her complex personality, her skills as a healer and a fighter. For example, it could show how she balances her gentle side with her fierce combat abilities.
You can start by looking on fanfiction platforms like FanFiction.net or Archive of Our Own. These sites have a large collection of Bleach fanfics, including ones centered around Captain Unohana. Just use the search function and type in 'Bleach Captain Unohana' to filter the relevant stories.
Some Tumblr blogs dedicated to 'Bleach' may also share or recommend good Unohana fanfics. You can search for tags like #Bleach #UnohanaRetsu #Fanfic. Additionally, joining 'Bleach' - related forums or communities where fans discuss and share their favorite works could lead you to some great Unohana fanfics.
In a more complex way, their relationship could be one of growth. Unohana's calm and collected nature could influence Ichigo to be more patient. At the same time, Ichigo's bold and fearless attitude could inspire Unohana to be more adventurous in her approach to things. This mutual influence could lead to a deep and meaningful relationship that evolves as they face different challenges together in the fanfiction.