It's obviously bait if what we've seen about her character so far is any indication.
This doesn't stop Kei from inventing a retarded and out of character reasonings to break them up however. Relationship progress this early was always destined to fail anyway.
If it's up to Sasuga, she would make Hiromi's ex get through Green Goblin-induced character development, accept she won't get what she wants with other men with the "3 highs", neither have a happy life trying to use MC as a provider while she goes to ride the cock carrousel, realize MC is where she belongs, baby trap him so he can get the hint he is who she wants to definitely settle down with and have them ending together for real, but having to cohab with the other girls who will have better and chadder boyfriends or fiances until the moment they find a stable job.
So the meaning of the series title "Can we live together?" comes full circle. At first it was about MC asking those girls to cohab with him, but in the end, it will be about the ex asking him to live together after realizing she hit a big wall, is on a godfucking deep quagmire, nobody will give her whay MC gave and that she has to earn by herself everything. Mw the cohabitation chicks take turns helping them with raising their kid.
Got that dark epiphany after rereading the chapter where MC told his ex to take a hike after finding out her true intentions of her return. That moment is gonna be that bitch's canon event.