Mamiko Noto will play Kojiharu, the 8th-generation idol to assume the name of real-life AKB48 member Haruna Kojima (also nicknamed "Kojiharu"). Ryoko Shiraishi will play Takamina, the 5th-generation idol to assume the name of real-life AKB48 member Minami.
I wish JT would properly refer to her as "retiring", "moving on" or even "quitting". I know in Japanese they refer to this as "graduating" but I really wish they'd use the proper English terminology here since this is an >English< news source. I get a kick.