Toi Ichi, Eien no Ai wo Shoumei seyo. Heroine Hosei wa Nai Mono to Suru.

That day, I was going to confess my feelings. I was going to confess my feelings to Nagisa Tokiwa, a kouhai who has confessed her love to me many times. Alone on the rooftop, I was supposed to tell her how I felt and finally become lovers—but I got caught up in a "Confession Quartet," a game about love and romance. If you fall in love during the game, you are promised "eternal love" by the power of magic; but if your love is not fulfilled, it will be as if it never existed in the first place. In other words, the relationship will return to the way it was before you fell in love. "I want to cherish the process of love with the person I love, without the guarantee of eternal love." "If I can't have eternal love, I'd rather forget this feeling altogether." In the face of such an ultimate choice, I start to defy this game. (Source: Official Website, translated)