妹なんですけど。

From Author Wars - https://authorwars.com/publications/mei-nandesukedo-551822.html

Overview:

Title: 妹なんですけど。
Author: 榊一郎
Year: 2006
ISBN-10: 4757728670
Publisher: エンターブレイン
Pages: 275
Binding: Paperback
Type: Novel
Title Reference: 妹なんですけど。
Notes: Data from Amazon.co.jp
Cover artist per cover credit
Title transliterates as "Imouto Nandesukedo." (Actually, I'm Sure It's My Younger Sister.)