THE ONE YAMABUKI IS FINDING WAS "LEMON CHAN"
Not a spoiler*?? Just a guess
since she asks yamabuki to help the club be professionals, also she wanted to be hidden since there is a age gap as she knew it wont work out and yamabuki told i loved you to a teacher.
well just my guess and i really have the gut feeling it was Lemon
𝙺𝙸𝙽𝙶 𝙾𝙵 𝚃𝙷𝙴 𝚂𝙾𝚄𝚃𝙷𝙴𝚁𝙽 𝚂𝙴𝙰𝚂🏴☠️🐋
close enough . write a novel