This Girl He Only Met In His Dreams

Bertholdt Hoover is empty. He doesn't remember the last time he felt alive. Every day is the same. Wake up, go to work, sketch at the park, then come home and go to sleep. The only time he feels truly alive is in his dreams. He dreams of this whole different world where he is whole and complete. He has dreams full of familiar faces that he's never seen before. And most importantly, he dreams of this girl. A girl that he's deeply in love with. But what is her name?

(SPOILER WARNING, some manga spoilers)