Don't forget final blushing and hugging! There are kisses. With Choko's lips it's obvious Mitsumi was kissed and with Hana's face it's implied Mitsumi was between two kisses!! Choko and Mitsumi established mutual affection. Mitsumi is visibly polyamorous. One poly vertex makes this now a polyamorous triangle.
Where things go from here is open to interpretation of the last two pages. Does Choko's "It's okay with us" mean just Hana's plan or the results of being free with your feelings in general, where Choko's feelings apparently grew poly? My interpretation of the gag in the last panel: Hana and Choko seem to be in a kind of competition for Mitsumi because Choko seemed slightly jealous, Hana seemed oblivious, and Mitsumi was stuck between them with a sweatdrop like a sighing harem protagonist. This could have made a good short series.
No one is pressuring Mitsumi and Hana to become polyamorous but with Choko established poly and the happy tone of the ending, a proper triad could happen. Realistically Hana risks becoming the third-wheel of the newly-mutual Choko-Mitsumi pairing. A girl who loves you stole your girl, damn. Losing a girl you love because you also love her girl, damn. A mutual love won't be lost as easily.