Hey there! I followed this questions before and it was really education and informative. You can also contact/message the person if you have more questions :)
http://www.mangago.me/home/mangatopic/5929808/
A user asked the op about which manga is closest to realistic and this is her answer:
I can't off the top of my head think of a REALISTIC one per se, but I'm currently reading this one called "Private Lessons". It's not perfect by any means and especially at the beginning there's some sketchiness in the dynamic, but out of the ones I've read recently it's on the more realistic end of the spectrum :)
Hi! I’m writing a BDSM fanfic. Any recommendations of accurate portrayal of BDSM in manga or webtoons? Doesn’t matter if it’s BL, GL or straight.