Mitsuki is chasing Meroko's doll in the final episode. The doll leads her to a familiar looking young musician. Mitsuki recognizes him and tries to call out to him, but she'd just had the surgery on her throat needed to save her. Then the boy starts to walk away. Mitsuki finally shouts at him, he turns around and suddenly it all comes back.
The manga has the revelation of why Mitsuki can see the Shinigami. Eichi's ghost never left her, and it's through him that she can see them.
Mitsuki: Between [Meroko's] hand and mine... is Eichi.