It seems to be Kasumi. She has significantly longer hair than Komaki does and the braids that rest on her breast are tied with white ties. Kasumi's breasts are also somewhat larger than Komaki's.
On a side note, it's somewhat hard to tell whether Yumi, Hisa and Sumire have already been genderswapped in the lower right hand corner, since Yumi's suit looks very much like her school uniform, and Sumire seems to wear a blazer and necktie for her winter uniform.
Usuzan High School
Pictured: Iwadate YuanLive Announcer
Pictured: Hariu EriCoach / Adviser
Pictured: Akado HarueArakawa Corps
Pictured: Shimozuki ItoGood-Looking as Guys
Pictured: Kajiki Yumi, Takei Hisa & Hirose SumireKentani High School
Pictured: Morigaki YuukaAchiga Kid's Mahjong Club
Pictured: ???Professional Commentator
Pictured: Kainou YoshikoShindouji Girls High School
Pictured: Shirouzu MairuMiyamori Girls High School
Pictured: Kosegawa ShiromiBansei High School
Pictured: Kobashiri YaeKoshigaya Girls High School
Pictured: Asami HanakoHimematsu High School
Pictured: Atago HiroeEisui Girls High School
Pictured: Karijuku TomoeSenriyama Girls High School
Pictured: Onjouji TokiRinkai Girls High School
Pictured: Choe Myeong HwaShiraitodai High School
Pictured: Miyanaga TeruTsuruga Academy
Pictured: Kanbara SatomiKazekoshi Girls High School
Pictured: Fukuji MihokoRyuumonbuchi Highschool
Pictured: Ryuumonbuchi ToukaAchiga Girls Academy
Pictured: Matsumi YuuCharacters from Each High School that I'm Rooting forKiyosumi Highschool
Pictured: Miyanaga SakiTakatoubara Middle School
Pictured:
Murohashi Hiroko