While reading the post about classics at Nigorimasen, I saw a rotating banner with Manabi characters. I encountered it before, Nigorimasen's rotation pool is not vast. But now that I am the number one Manabi fan, something bothers me about it. Who is the extra girl on the left?

She may be some kind of manga-only character.

UPDATE: The consensus seems to be that it must be Momo, arrived at by the way of exception and deduction. Even Damien and Jeff wrote in. Jeff, in particular, mentioned: "Actually, she IS the Fifth Beatle in a way." Exquisite. You guys can stop beating me up now, but admit it: she looks nothing like herself here.