I have no idea who Koike (小池) is. Also, I'd like to keep terminology consistent with the subs but I can't remember how they translate 大将戦...
This is reaaaaaly but koike probably refers to the three ikeda triplets, kana's little sisters
Huh?We're right here with you!Coach... Koike...!That's right... Kana-chan can't give up now!After all... Everyone is here to cheer me on!Riichi!!FINCoach, who are you mailing at a time like this...?We'd rather be there to support you directly, but since Dad is out, we have to housesit...Koike...All right...You just wait, Koike!Wait! Coach?Don't give up, Ikeda!