oh, so you finally re-updated the previous chapters which where with very low qualiity....must been a pain and nearly a Sysyphis' work.. hope you took a rest to deal with few couple of chapters...
....so Shirabishi Rin had made company-playing and go along with a girl (Shinmiyouji Rei) almost same age as her real sister (Shirabishi Kyouka)... yet Rin "bullied" Kyouka...
that name "Ли́лия Алекса́ндровна Подкопа́ева" is probably based on this person, who is Ukrainian.... https://ru.wikipedia.org/wiki/Подкопаева,_Лилия_Александровна
so Hachinoi Eiji really is the original, since he knows the past of Shinmiyoji, and Urashima Eiji doesn't know very much about her (as gloomy girl what he describes in chapter 1). Curious when Rei discovered the double personality of Eiji, seems she care for Urashima.
Oh, and I think actually...
I'm considering SL as an isekai, because basically the main male character was actually resurrected. Baka-updated also consider this as an isekai (reicarnation).
https://en.wikipedia.org/wiki/Isekai in other words, Solo Leveling partially is an isekai.
Rorik of Dorestad is based on this personage - https://en.wikipedia.org/wiki/Rorik_of_Dorestad ; as there have suggestion he is also Rurik who is alleged to be the founder of Kievan Rus (this country actually have nothing with now-today Russia, whose origin is from Moscow).
And the Battle of...