https://www.dlsite.com/books/work/=/product_id/BJ229517.html
https://book.dmm.co.jp/detail/b164aisis01205/

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group: FeeedTL [email protected]
commissioner: espeon https://gender.tf

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If I'm interpreting it correctly, these two lines...

P.2 "He completely changed after 'that' incident and became super depressed." with a photo showing the dark-haired guy with his sister
P.14 "Have you gotten them back? Your real memories."

...imply that the dark-haired guy's sister was killed some time ago and made into the skinsuit by whoever owns that "workshop", and it changed him into her once he put it on. That's kinda creepy.

Base +34, Cadavrus +6, silv1 +6, MaskedSeamstress +5, slimedog +10, akseyd +6, Thanks +7, zykyne +7, adsemnij +6, randomname12131412 +7, Scarlet99 +6, 取名难啊 +6, Ildzmer +7, and 7 more...

It seems Yanaka kinda knows what's up, maybe he planned this.

Base +6, Thanks +7, zykyne +7, adsemnij +6, Ildzmer +7, Lesamuen +8, Captian Katsura +7, just Zombie +5

@meow_pao going off that and the other dialog it's looking like the blonde friend was dating his sister, but then she was turned into a skin (presumably by him). And now he's brought her brother to the cabin where the skin is kept, and he's now used the skin to bring her back to life by turning him into her. So, basically killing him to get back his girlfriend.

I'm not 100% sure if the narration at the beginning is the friend or the brother, though.

Base +12, slimedog +10, Thanks +7, zykyne +7, adsemnij +6, Scarlet99 +6, Ildzmer +7, Lesamuen +8, Captian Katsura +7, Saa-Chikou +9, just Zombie +5, xaelath +6

Well . . . starts reading . . . this would be the perfect set up for a horror movie . . . last page OOKKKK it IS a horror movie.

Base +6, masterzelda123 +6, Ildzmer +7, ElisaG +17, HiddenAgenda +8, bob620 +6, just Zombie +5

should've checked the weather forecast and carried an umbrella, doopid

Base +9, leafduo +6

It looks like it could work as being in the same universe as DATE Deep Stalker series.

Base +6, Scarlet99 +6, ElisaG +17

也就是说他妹妹说是意外，实际上是被做成了皮吗
我不知道为什么想阴谋论一波，实际上是基友干的，故意不带地图也是为了让一切看起来像是巧合

Base +6