Well, this turn of events was certainly obvious from the beginning. Mayu lying to her best friend is a big no-no and will certainly come back to bite her in the ass. Haru's New Year's card to Megu certainly seemed to have more emotional attachment than the one Mayu received from him so perhaps it has been Megu all along that he's liked. He did have her address, afterall. I wouldn't mind if Haru began dating Megu so Mayu could learn from her blunders.