Reading this back over, I'm kind of wondering if Yoshioka was experiencing comphet to a degree. That's not to undermine her potential bisexuality (I am bi) and it's not to undermine her potential for being poly (I'm dating someone who's poly), those are valid readings of the story. This is just a potential alternative way of reading it.
Yoshioka was seemingly never satisfied with men, and she never had a romantic relationship with any she had previously been with that we know of. It looks as though those relationships were purely sexual. We don't know how she engaged with men either, but we do know how she engaged with Yuka. Yoshioka was the instigator, the "top," I guess you could say, and Yuka always goes along with it and in doing so, took on the more traditionally "feminine" role. Yoshioka had moments where she'd mention that Yuka - in being stereotypically "feminine" - was making her horny, and for her to not sleep with anyone else since moving in with Yuka, she's clearly being satisfied by Yuka sexually, and possibly romantically too.
It's something that none of the men Yoshioka saw ever managed to achieve, which makes me wonder, was Yoshioka mostly seeking male attention out because the attention made her feel good, but because she is actually a lesbian, the sex was never fulfilling in the way that it is with Yuka. Kind of like, if anyone is familiar with the lesbian YouTuber Alayna Joy and her story. She mistook enjoying attention for sexual attraction toward the opposite sex, so sought that out, but now that Yoshioka has experienced a lesbian relationship, she is only just now coming to realise her own feelings and her own capacity for romantic and sexual attractions that are more in line with her "true" sexuality. Lesbianism likely wasn't even on her radar as an option until Yuka, after all.
Yuka had her "a-ha" moment in the first chapter, but maybe this "I haven't seen anyone else since moving in with you," thing is the beginning of Yoshioka's "a-ha" moment. The relationship is still early days, it would be nice to have another chapter from Yoshioka's perspective as she realises her feelings for Yuka more and more.