Ohhh, ... Kayyy - we'll for the moment discount the 'hentai logic' that would permit Mizuki to purchase such sexy lingerie online (who's credit or debit card paid for that?) or that Shuuichi's horny switch gets flipped so that he's compelled to drop his pants and jack off in broad daylight, even in his living room of friend's home, OR the biggest logic bomb of all; Shuuichi and Mizuki are able to engage (so-to-say) Phase 1 of their sexy time with Shingo being none the wiser.
Logic or lack thereof notwithstanding, Well Isn't That Cute, ... BUT IT'S RIGHT!
Ahem, [pushes glasses up nose] I believe you'll find that some parents give their children credit cards or their own bank account (with debit card). Lot of reasons for this, such as teaching about saving or making sure your child has money for emergencies. Also, some parents just let their kids use the CC instead of giving them cash, then they get to track the purchases.
Yeah...It starts with an appreciation for porn of an actress who looks like your friend's cute sister.
And then it goes on to tutoring where they study together(read:have sex).
"How can I resist"? Well...You don't.
I have to say though that his friend is quite a nice guy and brother. First, an unintentional wingman by way of needing to take a leak, and after that, getting worried about his sister to the point that he's willing to run out and buy medicine for her.
Well hey, at least our protagonist now has more reasons to come over. Next thing you know, he's going to go from best of pals to brothers, literally.
Read this story and three thoughts popped into my head:
1. Why isn't there a Yahiro Pochi book on fakku?
2. Will this story get a sequel?
3. The first time her brother left as they were watching the porno he most probably went into his room or the bath room to jerk off