I don't like making NTR's hopeless.
You and Makoto, aka Mako-chan, are friends since your early childhood. You just confessed your love to her and she said yes, so she's officially your girlfriend. Originally, you would go your separate ways after walking her home, but instead, you realize you're holding her notebook. You decide to turn around and head to her house. Her parents happily let you inside and you head up towards her room, but as you approach you hear strange noises. Curious, you quietly open the door just a crack to peek in and you are bewildered by what you see. Her brother's friend is grabbing her breasts, she's giving him a bewildered look but isn't stopping him.
Her brother's friend is reaching for his zipper. You don't know it, but a small thought in the back of her mind is liking the erotic nature of the situation, but that thought will soon grow if this proceeds W-what are you-?