32 but only 16 with missiles in peace time/installed seems as had been said by Samurai and confirmed here
So
16 cell's armed : 12 Asroc VL and 16 ESSM as Hyuga
or 32 : 16 and 64 as Akizuki
Japaness combattants have in general much cell's for ASW missiles the max for Atago 32 on 96 ! according Flottes de Combat or reliable sources ofc missiles load can change...
On the other hand even big DDG embark " only" a SH-60K or J the K is bettter armed also with small anti-ships missiles, used by the more modern classes, 91 ( 49 + 42 ) with 75 P-1/3C a robust ASW force !
And even if only 16 cell's host missiles in general with yet 4 Mk-41 installed they can get fast the war load, Europeans and i do face palm have provisions for majority of recent classes : Horizon/Type 45 : 16 cell's, De Seven Provincien : 8 etc... but we can wait for see it instaled ! ofc in relation with this part of the Asia which is since several years about 10 the main naval theater...