https://www.dlsite.com/books/work/=/product_id/BJ303173.html
https://coolmic.me/titles/3241 (English)
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Worst Day Ever: Invited to My High School Bully's Bachelor Pad

Nooo... I already came... Please forgive me... Forced to kneel with my face to the wall, I can hear the sound of my girlfriend struggling against the sexual advances of my high school bully. "Haha! Your girl's clit is way too sensitive!"
She starts to breathe heavier, and I can hear a wet, squelching sound from behind me. "She came again! Soon she'll be begging for my cock!" He talks loud enough for me to hear every little comment he makes about her. Just what did we do to end up here...?
I brought my very first girlfriend back to my hometown to visit, when the worst possible thing happened! We were out on a date and one of the scary seniors who used to bully me at high school saw us... "Come hang out at my place... and bring your girlfriend!"
The guy's a notorious womanizer, so I had a bad feeling about what'd happen if we went with him, but I just couldn't say no...

Japanese RAW (Chapters 01): /g/2662342/a46e2754ed/

Checked the raws.
Different heroines, 3 chapters each at most, he leader of the rapists is a faggot, whenever he's facing someone as strong or stronger himself he either monkey punch, tases them or threatens them by using their lovers as hostages along with his gang.

Base +20, Fofotron +17, mofalcon +6, calorimetry +9, anonymousMember +6, Porokichin66 +9, rjimenez666 -6, breanyman +6, HoodieGuyLairud +6, MeloTheYellow +6, shinnt -20, itspherical -6

On the bright side, whether or not the MC wants it, the relationship is def over, so she can keep fucking the piece of trash and probably ruin her life, while the spineless MC can either learn from this and be better, or at least die alone comfortably.

Base +6, Fofotron +17, Zakuzelo -14, rjimenez666 -6, barkingdead +6, HoodieGuyLairud +6, shinnt +20, zukuenft -9

i think this is too cruel for the girl

Base +6, rikudosennin -6, ShinKagami +8, Weisschen -6, Vormik -7, shinnt -20

And today's award for "Dumbest Hentai Protagonist" goes to...

Base +6, Fofotron +17, barkingdead +6, Vormik +7, breanyman +6, MeloTheYellow +6, DesRed +6

There's a limit to how spineless you can be, right...?

Base +19, Vormik +7, breanyman +6, MeloTheYellow +6, shinnt -20

They aren't stealing her, they are a fun fling from time to time to be enjoyed. This could work for a loving relationship. ;) Just not very common, lol.

Base +9