Oh, and Marika isn't saying she doesn't love him romantically. She's now sure her feelings for Sawa were never romantic because of what she feels for Hachiouji, but she doesn't have a name for (or is afraid to put a name to) what her feelings for him actually are.
What she says is "It's less that I like him and more that I suddenly feel a sense of attachment to him." And when Sawa asks if she means "it's love not like," Marika responds "Uh, not exactly... It's hard to put into words." And she later asks "What is love, anyway?" While it's possible she's "afraid to put a name to" her feelings, I don't really see why she would be now that she's fully explicitly dating him.
Also, I very much disagree that she's sure her feelings for Sawa "were never romantic." They're not romantic
now (supposedly), but
in chapter 23 she reflects that she definitely used to have something very similar to romantic feelings for her; she just (supposedly) doesn't anymore. And on Sawa's end, I'm not sure if "bothered by having less time with Marika" and "feeling inadequate" really explain her obsessing about seeing them kiss for an entire day and then slipping so hard she breaks her hand lol.
To be clear, I fully expect this manga to end in double het. However, theoretically, if the author were trying to set up a twist SawaxMarika ending, this is
exactly how she'd do it, with Sawa displaying jealousy she's literally never shown before and Marika
still not figuring out what precisely she feels for Sawa and Hachiouji. And while I am admittedly a yuri fan, I stopped caring about any of these characters a while back so such an ending wouldn't really make me happy. However, it would be extremely funny and piss a lot of people off, so I am rooting for it for that reason.