Low-key I really want Eiko to get major character development and start to rank up as an attempt to catch out to iruma. I would LOVE to see more of her
I'm imagining her disappearing for months or years and comes back as something like the Green Ranger to save the day and be an antihero. That'd be fun.
Could get isekei'd to the human world get epic adventures, then get back to the demon world finding that little time has passed.
Those would allow a fun side story and bring her back into the main cast afterwards.
I don't think this author has any boundaries for how crazy things can get.