Likely the same husband/boyfriend. Ooi's lines ("I love admiral, TOO",) most make me think she's bi and completely receptive to purchasing multiple rings for provisional marriage harems, just so long as she gets a slice of the other wives.
(That or IPS cells and lesbian wedding, as previously mentioned...)
Perhaps the man Ooi had a child with is no longer with her as he isn't mentioned in the description. What I think is more likely is that since KTKM was in a relationship with someone, perhaps she had to come to terms with that and move on with her love life. Maybe the Husband was someone who was always beside her but she never noticed, so when she felt the need to love another as much as she does KTKM, the choice was obvious.
Ooi... it's nothing, we're meeting by everyone in front of Mamiya's.Yuubari? What are you doing in such a place?Whaa... it's cold todaaay...❤ Wait for me, Kitakami-swhaaann! ❤Tha... Thanks...It'd be better, if you waited inside.Hmmm?Kitakami-san ❤Yano ToshinoriBy the way, you're dressed too lightly for such a cold weather, Yuubari.Ooi
A girl that loves Kitakami-chan as much as she does her parents.Um-Yuubari-san, waiting for everybody.
(*Samidare had forgotten her wallet, so she turned head over heels and went back to her company.)You can give it back whenever you want to!Yes, yes, same ol' huhWell, if you don't stand in the way between us and Kitakami-san with her daughter, I'll say whatever.Kitakami-san ❤She's thoughtful for some reason. That Ooi...Cold is a woman's archenemy, so dress appropriately!Ooi (30)
Started her own fashion brand "Oi". Is active as a designer.