Substitute Girlfriend ~I'll Become a Slutty Gal to Protect My Best Friend!~

"Wait, Sui-chan... You got a boyfriend!?" I received a shocking confession from my best friend, Sumi Mizuki, that she had gotten a boyfriend. And to top it off, her partner was none other than the popular and handsome Matsui Tatsumi at our school. At first, I was celebrating Sui-chan's relationship, as she was my only friend at school. However, I gradually began to sense that her appearance and behavior were changing for the worse. Spoiler In the midst of this, I learned that Tatsumi was setting a trap for Sui-chan, intending to turn her into a slutty gal. To protect my precious best friend, I confronted Tatsumi and demanded that he break up with her. "I-I'll be blunt. Please... break up with Sui-chan..." "Huh? Because you're feeling lonely after losing your best friend, you want her back, huh? Lol" And the condition Tatsumi presented was to offer my body as a 'substitute' for my friend. Driven by Tatsumi's love for slutty gals, I was coerced into numerous perverted acts, transformed into a slutty 'substitute' both in appearance and in spirit. Before long, I found myself sinking deeper and deeper into this abyss, becoming nothing more than a 'substitute' in every sense. (TRANSLATED FROM DLsite)