This is pretty apt given the latest chapter, 187, which seems to be setting up a redemption arc for Minami while ending on a note of Sachi, someone that seems to actually love her for being a huge jerk, staring wordlessly at her interacting with a new group of people. We may finally be entering the yandere lesbian arc.
^It's... complicated.
The gist of it is that Kiara and Calli have known each other for millennia, being a phoenix and a reaper, and they've become good friends over time. Kiara is completely smitten by Calli but Calli is a classic tsundere and always keeps her at an arm's length but Kiara is slowly chipping her way into Calli's heart. Although things are going to get rough since Kiara is leaving Japan this month.
^ adding to this:
Calli has implied Kiara has died many times and doesn't always remember everything.
I like the theory about why Calli has a bridal veil they did get married in a previous life but Kiara never got that memory back after reborning and that's why dad doesn't want to admit her love, she doesn't want to be hurt again :(