Honestly, I am now expecting this manga to go in the direction where Kenji accidentally gets his gender changed and that allows our ntr chad to plow his best friend.
Now it wouldn't be ntr isekai without ntr. So while they're fucking it's revealed that kenji has a girlfriend on earth but unbeknownst to him she got isekaied as well. Leading to a fight between the ntr chad and the girlfriend over kenji.
And then we begin the cycle all over again. Though in this cycle, kenji fucks the girlfriend in order to protect kenji leading to kenji and ntr chads' fight again. And so they repeat again and again...