...what a stupid second part...
If MC did that to distract them so that Saru could move in a moment when he wasn't focused on coutnering it woudl have been good, but it was so to push the idiot to a suicide mission, is very bad writing, would have been better if after she moved on his neck he surrounded and his party decided to run away, knowing their skills aren't enough to defeat her.
The idiot had no reason to follow MC words "I will give her to you if you beat the dungon boss", why would the retard think MC was the party actual leader? In the "mediation" Saru was the only one what word had any power.
And again, is a stupid development as someone that is forced in a party like that is a terrible member and is more likely to backstab you for daring to blackmail her, not to count how once out the dungeon she could report it to the authorities and even if they don't follow up, leave for good.
A narcissistic idiot would have been better than this, could have said he is more prepared or levelled up and now they can continue and she doesn't have to stay with weaklings, still a weak chapter but better written.
I presume it comes from a novel and there is written better or the idiot tries to get back before doing this choice after feeling pushed to a corner, as this is another problem, after she left his first and only attempt to get her back is to blackmail her with innocent people lives?