Everybody is shocked after hearing that Master Suo plays karuta with 28 one-syllable cards.  Chihaya, Arata, Taichi, and the other karuta club members do some soul searching as they attempt to move forward.
In other words, there 
are 21 additional cards
Es decir, ¿hay 21 cartas adicionales
Es decir, ¿hay 21 cartas adicionales
Em outras palavras, 
existem 21 cartas adicionais