Kojima Haruna. She's been hinting her graduation for a while now. She was most likely gonna announce her graduation during the election, hence her speech but decided not too because of the Iwate incident.
I think,the 次 member who will announce her graduation is Kawaei Rina,because there's a time,before the last senbatsu sousenkyo,she send a short message to the ファン that she has something to say but she don't want to expressed it right now,maybe it will be her graduation.althought the short message was predicted to,as one of reason to the " Iwate Incident"
