Sense and Sensibility
This could have been called NTR the Shoujo and it would have fit better probably, at least based on the first story.
How much are you in love with your boyfriend? Do you love him so much that you'll fuck his brother? Do you love him so much that you'll lose your virginity to his brother? will you do all of the above while your boyfriend is in the house?
If the answer is yes to all, then you're just like Aya-chan and you really, really love your boyfriend, you just are a poor indecisive girl who can't pick between whipped cream cake and chocolate cake, you just have to have both of them!
After the main story there are 2 other stories about love, but I didn't bother reading them yet. After such a delicacy from the first one I don't think the others could compare.
As an addendum, I'd say this was the first Hina Sakurada manga I enjoyed more plot wise. although it's only the 3rd book of hers I read, the other 3 felt less structured, especially the first two,
The Flower with the Knife and
Dead Friend's Love Letter which felt a lot like all style and no substance (the art in them has an interesting style to it but it's not enough to carry the story), while
Taro is Distorted had some interesting points, but this delivered much better.