Right after Eiji knew what had happened to Ash when he left for Japan, he packed his bags immediately and went back to New York.
Ash and Eiji were an inseparable pair. They did everything together. They went through a lot and were each other’s comfort when the world around them seemed to be crumbling apart. Ash, especially, never had a person to confide in until he met Eiji. He made it his life’s mission to protect him and keep him safe, and once Eiji’s safety was guaranteed, death came knocking on his doorstep like it knew the perfect moment for him to die.
In the Banana Fish anime, it was never shown what had happened to Ash and Eiji after the events at the New York City Library. The anime didn’t even confirm Ash’s death, it just simply showed a panel of him being woken up by the librarian, but to no avail.

However, in the manga originally written by Yoshida Akimi with the same name, we see what happens to Eiji after Ash’s death. The panel after the events of the library features a time-skip. Eiji Okumura, now 40 years old, in his apartment in New York, with a golden retriever by his side. Hair reaching his hips, still ebony black as it had always been.
He still had the same people around: Ibe drops by, and Max and Jessica, now with their grown-up Son visit him. But now, he spends most of his time with Sing, who feels like he has such a huge debt to pay to him.
Eiji lives in New York, he is now a professional photographer. He holds exhibits whenever he can, and he gets help from old friends and colleagues. Eiji’s work is recognized by many, and his talent is seen as world-class.
However, in this last exhibit, he chose a particular topic he has held hostage–hidden for a long time: Dawn. Never once, since he came back from Japan, has he opened the drive that contained pictures of him.
It was too painful, even after enough years had passed. But during the last panel, when everyone had left the museum, Eiji sat down right in the middle of the museum, drinks by his side, fronting the reason for and the main attraction of the exhibit: A portrait of Ash, sitting by the window, right at the break of dawn.