A dark skin, tsundere sister appears and she doesn't get any action? Hope there's a sequel! Really though, this was good and I'm enjoying all of this artist's work.
I'm pretty sure Juri is in love with his sister. I mean, she gets horny everytime she hears the music of the sister and her name is Juri. Juri. You know, like yuri. Do we need more hints by the author?
Was your sister one of the DJs in that night? Did you meet her friend? Was your hentai protagonist switch turned on?
If you answered one of the questions with "no" then you can't really expect the magic to work...
Hmm, I was expecting his little sister to also get some action or something, but I guess not. This is fine too, though, I quite like it. He came to check on his sister and ended up being dragged to a toilet stall and fucked, so I'd say he had a good night.