Public announcement: We are settling in a new tg forum where we will finally be free of the conspiracy of hot pockets and the cults that follow Anita Sarkeesian's guidebook. Come with us and tend to our currently deserted island. http://tgboard.rf.gd/ Update for the move: https://endchan.xyz/tsf/
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Roughly: "Seriously a slutty hole~ To think my sister was this erotic!~"
Here's a typical blurb that I translated for no reason, since they're all nearly the same:
「Hurry up and thrust inside me....stir it up crazy!」――One day, in the warehouse the protagonist found a suspicious hole. While worried about it...he suddenly found himself in the middle of having sex?! Moreover, his partner was a boy?! When he looked at the mirror in confusion, he saw his older sister!Without getting what happened he was about to be molested, but a woman's body feels so good it surpasses the imagination...
Well since it's come to this, do what you like!! Having my openings teased by my bald coworkers.....my sensitive body is throbbing right to my slopping insides! Finally... my hole feels good being fucked and I won't let you pull out...!
== Some details from reading it: His sister is a bitch 24 (2 years older) who orders him around the house since he's a neet. So he goes to get a job and he finds a tunnel at his work. The first time he enters the tunnel he became an unknown women temporarily. The second time he goes to experience the pleasure again but becomes his sister and fucked by her handsome boyfriend. The next time he goes he hopes it'll be his sister again, and he realizes it is except she's ready to fuck someone else. He comes out right before he gets to come though. When he checks his phone he finds 15 minutes have passed, and surmises that's how long he can stay a woman when he goes into the tunnel.
(It's probably possession and it'd be very quick to translate if someone is inclined.)