Title: Ima Sugu Onii-chan ni Imouto da tte Iitai! Original title いますぐお兄ちゃんに妹だっていいたい！ Aliases I wanna say that I’m not your brother right now!, いま妹, Imaimo [Vndb.org][Official site] This is the reason why Imaimo is kami-ge by default. This is the art of Akinashi_Yu (春夏冬ゆう) who did Koi to Senkyo to Chocolate before this game. But the common route is not that good after the opening 1st hour. I have to do some amount of skipping in order to play this without boring myself to death. Also this game is not really prequel, it’s set in the same world and shares some characters. Chisato from Koichoco.
About the author
I'm the Fuwanovel community admin and a big fan of Visual Novels. The easiest way to get a hold of me is via a PM on the Fuwanovel Forums, by twitter (@ArchmageTay), or by email.