Dear women of the world, there's a whole lot of creeps trying their best in an attempt to coil you into their disposal, whenever you feel any of that under no mutual consent you must express your denial in clear & distinct way. Anything beyond simple "NO" is crime.
She keeps saying that these are based on real events but I'm not entirely convinced. For now my hypothesis is that she's going in a pattern of possibly true to probably a fantasy she had in the moment.
For example, I'm more inclined to believe that she gave her first time to a youngish park director rather than believe she hooked up with a stranger in an alleyway. I'd sooner believe that she slept with one of her friend's crush during a school trip than believe she had this positive reaction to a shady massage parlor.
It's worth keeping in mind that practically every demonic possession movie is also "based on a true story" regardless how over the top crazy they are—especially nowadays. There's always some artistic liberties and dramatizations added to make it a more interesting experience. Also this chapter in particular has a very ambiguous ending, questioning whether anything before the last few pages really happened, so I agree this might be more in the realm of fantasy than a 100% accurate retelling of actual events.
Ikr, most of her stories consist of situations many average would be traumatized of were they in her shoes. She might either be delusional with her weird fantasies or have balls to put up with all those irl.
Maybe somewhere Nagase-Sensei made it on an amateur AV film featuring massages. Her friend on the last panel isn’t to bad herself hopefully she too makes it on one of her naughty stories.