You left out " Femdom Erin: Pretends to hate Mars in front of the party, pretends to assassinate him, BUT behind the scenes he's happy getting lewded by Mars "Read this post from this summer to see where things are going post-timeskip:
https://f95zone.to/threads/hero-party-must-fall-v0-5-3-nitrolith.100153/post-14348963
This explains why Sera's curse is awakened regardless and other stuff.
Which is concerning for me, personally I'm hoping that Erin's whole public life isn't shit talking Mars and contriving obviously hopeless attempts to kill him. Like in that post it's acknowledged that the three main real girls are pillars of Mars' new society, they all have communities they lead and pursuits outside of being fucked by Mars. Erin doesn't have the same setup for content involving him specifically if he's just Mars' trophy/sassy pet.