Many mangaka get their start in fanwork doujinshi – Gen Urobuchi of Saya no Uta and Madoka Magica fame got his start in visual novels with a game based on the Christian Bale film Equilibrium. Yana Toboso of Black Butler is known for having dabbled in BL before beginning her long-running series, both in original works and in doujinshi.
Her original work, published under the name Yanao Rock, was included in several anthologies and spawned a tankobon of short stories, titled Glamorous Lip. In doujinshi she is likely best known for her boys love work about the characters from Prince of Tennis.
But did you know that under the name Shinjiku Glico, Toboso ran a Togainu no Chi fanart website, sold doujinshi, and even organised a convention? These facts, while not as widely known as her Prince of Tennis involvement, are still fairly easy to find – second-hand retailer Mandarake announced when they had one of her books in stock, and the same art of Rin can be found on an archived version of her professional website alongside her pre-Black Butler title Rust Blaster.
While it's still possible to purchase her doujinshi when they turn up on the second-hand market, her Togainu no Chi fanart website wasn't archived by the Wayback Machine, and only a few pieces remain findable online.
She organised the Dogs of Heaven Togainu no Chi fan convention in 2006, where a large number of doujinshi circles gathered to sell their work together.
A note of interest to those who read my entry about Death in Venice and the birth of bishonen – Yana Toboso cites Death in Venice as an inspiration for Lord Kelvin's obsession with Ciel in Black Butler.
As to whether we can expect more BL from Yana Toboso in the future, on Twitter she has said the following:
In the past I wrote works with the main theme of boys love, and I was crushed by the overwhelming difficulty. Regardless of whether it's opposite-sex or same-sex, I think works with a main theme of romance are incredibly energetic things. For me, the degree of difficulty is higher in writing romance than in drawing zombie battles or tanks.