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1) everything eren feels towards ophilia is platonic

Okay more serious answer. As far as canon goes, most of Eren's love is platonic - the expression he uses most often is that he would be most happy if the people he cares for could live good, long lives. Which is very difficult given the world they all live in. And the kind of shit Eren puts them through.

Basically, platonic love from him is hoping that people can live freely and getting real tears eyed when they can't.

Teary...eyed...this is why you don't write on the phone fellas

I don't play characters who woo others. At least not often. Eren is probably the worst offender in that he's gone the entire series without showing much interest in romance but it's in the subtext for erehisu that I try my best to make somewhat fair assumptions.

He stands up for Historia time and again whenever she makes tough decisions that would only ever bring her to harm. A lot of what he does is based around making sure she can live freely since he knows how hard it is for her to allow herself that much. It's a matter of priorities, he puts that one person above all others and says fuck you to the rest.

In a more traditional sense I figure he would spend more time with the person he's interested in than with others. Take them out and experience life since he's not got a lot left of it to live himself. If he wanted to really impress them he would try and play to their tastes but it would mostly be through what he does and says that expresses his feelings.