Author Ryusei Kaji's Unreasonable Love(2013)

K-sensei no Furachi na Junai

The aggressive Ryusei Kaji is a popular novelist. Midori Kobayakawa is his serious and timid editor who was forced into a relationship with him... The third book in the series about the constantly anxious editor who's loved by the passionate writer!

(Source: Renta!)

Note: Contains two extra chapters.