Amnesia,

you say?

That's right.

That summer when he was 18, he returned to his hometown and had an accident, you see.

Per the wish of his father who was an admiral that time, they performed on him a memory falsification we used on ship girls.

That "he had lived in Japan for 18 years," instead of the 18 years he actually spent with you.

And "he took the position of an 'admiral' at the age of 22."

You're now—

nowhere in his memory.