Well, from an autistic perspective - sleeping together is probably the most romantic people can get.
Most of the average "NT" dates usually take place in highly social settings, usually going out for dinner or something like that. Which, makes no sense from an autistic perspective; as the actual point of it is actually just to be with the person. This goes for both genders (At least I think so - it's highly likely)
As there's generally less for the senses to pick up when sleeping w/ said person except for the person themselves; I think it's probably the best.
I'm not going to deal with gender-specific stuff; as it just doesn't make much sense from my point of view - personalities aren't gender-specific, and it is subject to change from person to person.
That said; it's also the best setting for what I like to call "Enveloped in an Eternal Embrace".
(Keep in mind that this is largely speculatory; as I have never actually had a girlfriend as of yet)
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