Espanyol president Dani Sanchez Llibre admits Nakamura never adapted to life in Catalonia.
"It's a shame, but it's not a drama - I think it's a beneficial deal for both clubs," he said. "I have good memories of his arrival, and of his presentation, but unfortunately the player couldn't acclimatise.
"It's a question of feelings, the language, his family and children were far away, and he is about to be a father again."
Espanyol had planned to take advantage of their media asset with a summer tour of Japan, but look set to scrap those plans now.
"It's up in the air," Sanchez Llibre admitted.