The girl in the back is probably either Chigusa Maru or Zuiun Maru, Yamashio Maru's sisters that weren't completed during the war and were converted back into tankers after Japan surrendered. 

Yandere sample of https://yande.re/post/show/1051307

evvvk said:

The girl in the back is probably either Chigusa Maru or Zuiun Maru, Yamashio Maru's sisters that weren't completed during the war and were converted back into tankers after Japan surrendered. 

evvvk said:

Zuiun Maru

evvvk said:

Zuiun Maru

This isn't going to end well!!