http://bhm5koavobq353j54qichcvzr6uhtri6x4bjjy4xkybgvxkzuslzcqid.onion/rec/index.html
I've read some, or rather remember reading some during my isekai binges. The problem is that 90% of isekai is mediocre and occupies the same spot in my memory bank. Unless it stands out in a good way. This, this stands out. I would recommend Onee-sama to Watashi: Ojou-sama ga Isekai Tensei as a masterpiece "anti-isekai".