I like how the main girl isn’t the romantic interest of the MC in this but the noble girl who’s mostly the villain
Well to be fair, Eliza is supposed to be the main girl for Kururi. At the very start of the story it is stablished they got married in the bad end for the villainess and actually both of them fell in love right after meeting. Remember that incident where they exchanged correspondence? From then on Kururi only aimed at Eliza.
Iris was always the game's MC and prince Ark the main guy IIRC.
If you want a similar example: "Villager A wants to save the villainess no matter what", where the reincarnated guy becomes a mob character who falls in love with the villainess. It's a subgenre of the villainess story (shoujo story usually with a trope of Otome games) aimed at shounen audiences.