Jitsu wa Imouto deshita.: Saikin Dekita Giri no Otouto no Kyorikan ga Yatara Chikai Wake

My stepbrother, Akira, was introduced to me as a high school student when our parents remarried. He is a beautiful boy but shy because he grew up in a difficult family environment. I've always wanted brother, so I spent time with Akira for his sake, and... we hit it off right away, and we quickly grew close!

I asked him, "...Bro, do you like me?"
"Yes, of course."

Our relationship deepened despite a critical misunderstanding. Until finally, I realized that Akira was actually my "sister" and I became very confused...

"I liked the relationship between us when we were just brothers. But I wish we could be something more than that."

Akira's new approach, trying to make us "lovers" instead of "siblings," has begun! A flirtatious love comedy with an easy-going, too-cute, little-brother-like sister!

(Source: Kadokawa, translated)