Things like Matsuri saying that Harumin is too affectionate with Yuzu could be read as Matsuri's observations being clouded by jealousy. Even the cover of the story is Matsuri staring at Harumin in the hallway at school, plus Matsuri following Harumin around and spying on her could mean that it's Matsuri's feelings that might be love that the title could be referring to.
I agree with this. I don't think Harumin loves Yuzu romantically.