Adult PC Game: Wagamama High Spec - Final by Madosoft (Eng) Archive

The story revolves around Narumi Kouki, a high school student who also draws a manga serialized in a weekly magazine. Because the manga he draws is a risqué romantic comedy, he keeps this fact a secret from everyone around him, with his younger sister Toa and his sister's best friend Mihiro being the only ones who know.