Probably Katsuragi arrives in a good moment, specially to see the mature side of Zuikaku and not only the uke version, when she is in front of Kaga.

S_holmes said:

Probably Katsuragi arrives in a good moment, specially to see the mature side of Zuikaku and not only the uke version, when she is in front of Kaga.

Kaga sunk in 1942, Katsuragi launch in 1944. So i'm pretty sure that Katsuragi join after Kaga died, so Zuikaku look more mature.