Rei actually goes harder on this later in the LN.
Basically a lot of the LN spends time shitting on Japan's view of homosexuality and how she passes plays a huge part in that as well. The book is basically one giant middle finger to Japanese society masquerading as a cute isekai yuri romance
Alright, sooo
Risako's a sociopath and in love with Kaoru but being freaked out by this is like nope nope gonna burn everything down.
Lame guy is spineless as shit.
And Kaoru is now realizing Uta was the answer all along.
Kay then. We got somewhere!