Shin deserves WAY better than those bitches.
They're not shy about shoving their tits in his face or letting him touch them. But they won't speak up about letting him stay in the party.
If this was going to be a good manga, then Shin would replace them and move on. Sadly, the premise is set and it's just gonna turn into smut. It's just a lesser version of that milf manga.
Its going to break some common tropes so its not too bad.
The three women plan and then fire the Raid guy after they have failure after failure because they have been carried by the MC. After removing the idiot, they seduce the MC with their breast and the MC slowly relents and goes back to the party as the only male. Then they have seggs occasionally.
Unlike most "exiled from party" stories, the heroines aren't bad people, they just made a bad decision. "This feels wrong" and "did we actually do the right thing?" and "I miss him" were all sentiments that Lena and Nina expressed BEFORE they found out their party is weak without him.
But more importantly, they were deceived...
And the third woman, the newcomer Fana, was uninvolved in the decision and it bothers her from the start. She's more or less best girl at this point.
But of course, it's not like they are completely without fault, as they could have communicated more and been more proactive. However, them being partially at fault (but not so at fault you hate them) is the whole point of this story.
After all, if they were completely blameless, then he would just say "okay, I'm joining your party again!" and nothing would change between them. But it's exactly because there are hurt feelings and tension that HUGE BOOBS have a role to play in the story.