Welcome back, it's been a while!
Oh, Koi... it would be a lie if i don't understand what Koi is struggling about. She knows compare to Yura, she is inferior, and understand herself that her feelings for Nagi is heavy that she scared she would make Nagi pull away. And because she has such complex plus Nagi chose her second after Yura as trial lover that accumulated her anxiety and so through a request she was trying to engrave her feeling onto Nagi. But because she is a good girl at heart, couldn't do what could hurt Nagi and ran away. Out of the 3 character, Koi has the most realistic characteristic and easiest to relating to... 🥺