艦隊これくしょん -艦これ-
913 can be read as "ka-i-sa", as in Kamen Rider Kaixa, hence the code to activate the henshin. An anagram of this is 193. it was intended to be read as "ichi kyu san", but can also be read as "I-Ku-Sa" as in Kamen Rider IXA or Iku-san. In the former's case, this is the code to activate Rising Mode. In the latter's case, it also means Iku Nagae or IJN submarine "I-19" in "Kantai Collection".