I suggest a text change as real history quote.

"Look at the world, within the sea, there is no immortal."
-> "If the bird don't chirp, Kill it. Little Cuckoo." (鳴かぬなら 殺してしまえ ほととぎす)

It is one part of poem which describes characters of three Japanese legendary lord (Oda Nobunaga, Toyotomi Hideyoshi, Tokugawa Ieyasu) about "how will they do if little cuckoo don't sing".

Oda Nobunaga will kill.
Toyotomi Hideyoshi will make it cry.
Tokugawa Ieyasu will wait.