Is it just me or the club visit with with that annoying bitch of a character called Scarlet screams NTR!
Hmm...Scarlet to me is acting like a dangerous immature idiot, who has the potential to be a threat to your little sisters wellbeing with her foolish and naïve choices in the story. And the fact that MC is just allowing that young tramp to further corrupt his little virgin sis, would be a warning sign for some who are not into giving up control and sharing.
It would not surprise me later, that Scarlet would make further attempts to influence a situation where she would introduce her dad to your little sis, to corrupt her into a threesome with him. And for me, MC is such a pussy for not being an a better alpha protector for her, instead he is allowing that whore Scarlet to take full corruption control of his LI (and since Scarlet is constantly communicating her present and past sexual experiences with her father, seems to me she is actually trying to soften and corrupt your little sis to that route).
Sharing is definitely not my thing, and Scarlet's past and present behaviors definitely has an NTR vibe to me. Even though she doesn't have dick, scarlet is continually taking your LI's sexual desires away from MC, in order to further her own sexual agenda with his little sister.