In volume 4 White talks about himself as the lighthouse keeper; guiding others from afar and in silence while living his life alone, in fear of leaving that high tower.

In volume 6, and as pointed in chapter 43′s title “Drifting Sailor”, Black is the sailor. He has all sorts of tides, high waves, and crushing storms, yet he sails on riding the waves, sometimes ignoring them as a whole in a reckless fashion.

They’re both connected by the dark deep beautiful sea; their life.
And they’re both standing on the same land with steady legs that is their friendship.