Looks like the translator's got it already, but here's a brief synopsis, to tide anyone over until the translation is posted:
Shiori comes over to Takashi's place, for the usual reason. He tries to reject her, because his little brother's coming over.
She rejects the rejection, because that's how she is. She also thinks she'll get a real good climax out of showing off her dominance to the little brother.
He comes in; he's a trap, and she is totally smitten. He's exactly her type.
But she's in the middle of sex with Takashi. And she doesn't want this guy to see her like that. She makes the excuse that they're playing pro-wrestling, and retreats to the bathroom to clean up a little.
That's a problem, because she had to clench like hell just to restrain the emission to what little it was... and she should last another twenty minutes or so. The little brother enters shortly to check on them.
Shiori gets his name, Hikaru, and tries to make small talk (about his sexual preference, of all things). She thinks to herself that she'd like to knock him up...
She leaks. Then, mortified, she runs away.
Hikaru examines his brother. His thoughts reveal that Shiori did not fool him in the slightest. He knows what Shiori was doing with (to) Takashi, and surmises their relationship. He thinks she's a strange girl... but would like to see her again.
Omake: This is Pal Maison's first trap character, apparently. A highlight of Hikaru's profile is that his hobby is video broadcasting.
Back at her house, Shiori releases some sexual tension, but she cries in the end, believing that Hikaru surely thought her to be a strange girl.