Eromanga Sensei

Eromanga sensei (エロマンガ先生) is a Light Novel series written by Fushimi Tsukasa, the author famous for his hit series Ore no Imōto ga Konna ni Kawaii Wake ga Nai (俺の妹がこんなに可愛いわけがない, lit. My Little Sister Can't Be This Cute) and published by Dengeki Bunko (電撃文庫).

The first book in the series came out on December 10, 2013 by the title Imōto to Akazu no Ma (妹と開かずの間) and the second came out on May 10, 2014 and is titled Imōto to Sekai de Ichiban Omoshiroi Shōsetsu (妹と世界で一番面白い小説).

Also, a manga adaption came out in the Monthly Comic Dengeki Daioh (月刊コミック電撃大王 Gekkan Komikku Dengeki Daiō) in the July 2014 issue drawn by mangaka pen named "Rin".

Fushimi Tsukasa commented “I feel that Kirino from OreImo is a pure, innocent girl. This time, the heroine, Sagiri, may seem innocent, but she is quite dirty. I hope readers enjoy finding the differences between the two heroines.”

Plot
Izumi Masamune is a fourteen year old light novel author that is taking care of his hikikomori younger step-sister Izumi Sagiri after their parents passed away. His sister never comes out of her room except for restroom breaks and baths, during which he has to get out of the house. In fact, he's only seen his sister one time.

One day, he finds a blog written by the illustrator of his  light novel 'Eromanga' and learns that his twelve year old sister is his illustrator. Then, he later meets a young best selling author who wants Eromanga for herself and becomes his rival.

Izumi Masamune (Protagonist)
A light novel author who just wants to get closer to his little sister and get her out of her room. He has incredible typing speed and is a hard worker.

Izumi Sagiri (Heroine)
A shut in who is secretly her step-brother's illustrator (Eromanga) with out both sides realizing they it. She is an incredible artist and loves drawing perverted scenes.

Yamada Elf (Rival)
A young, beautiful light novel author who suffers from Eighth-grade Syndrome (Chūnibyō). She becomes the Izumi siblings neighbor and wants Eromanga to be her illustrator.