There is really panels of emotional and physical cheating and in this story... guiding in particular kinda blurs out the lines of their sexual acts which if seen in our view as a reader, it is cheating which makes your point valid. Even if in their world guiding is seen as a duty; being in sexual connection to another person is definitely cheating.
But I guess I still like to continue to see how things will unfold. If ML will disclose this to MC and will have courage to break up cleanly with his gf which idk why the hell he is with her..
Guideverse mentality is weird since it really tries to blur out the boundaries of sexual contact as a call of duty with no emotional attachment involved type of shit. Another example of this weird dynamic is from Dazzling breath but not the main characters but the side characters which involves MCs family.. For short: MC sister is married to an esper but her husband is having sex with her father and other guides.

Everyone who likes this story is hella weird. Don't call ml a green flag since he is definitely not, and idfc if gf is cheating too or cheated "first" mf ml is a cheater too and that's what matters. But ofc the readers who love this doesn't care since as long as the uke is not getting cheated on it's all good. Disgusting (/TДT)/
I feel so sad ugh, I fr thought I finally found another new cute story AND the guide is the seme... But nope... Ofc ml has a gf and he doesn't care he's cheating too, the author truly made him very "green flag" alright