I think the romantic aspect is there, but is not why he’s drawn to her. Instead, I think the romantic tones to their interactions highlight how disturbing and twisted their relationship is.
What draws them together I think is all of their similarities. He was drawn to her writing before he even became a ghoul because he recognized his own feelings there, he could relate to her loneliness and the way she expressed herself.
After becoming a ghoul, they only became more alike, and he even followed her down the same self destructive path, until the only thing that he could relate to and enjoy reading anymore were her books.
And now, he’s become even more like her. And they both know it. She told him so, probably to draw him closer to her, but also because it’s the truth.
That’s also how she knows he wants to be loved, and why she used that against him during their fight, in order to secure his attachment to her even more.
As for why he’s attached to her despite everything she’s done, he has a history of attaching himself to female figures who hurt him, and especially those that resemble his mother. See, Rize. She tried to muder and eat him, she laughed in his face when he tried to escape her, and she was the start of his traumatic ghoul life.
But he spent most of TG looking for information on her, or looking for her. And when he finally met her again, he cried in front of her and begged her to recognize him. After everything she did, he still attached himself to her, and just wanted her to acknowledge to him.
I think that’s definitely tied into his complicated relationship with his mother. And I think the same thing is happening with Eto.
Only, Eto is aware of the unhealthy attachment, and she’s using it for her own ends.
Relatable FE Quote or Something 