Ethan is all tense muscle under dark skin, which Edward was only halfway expecting. The muscle was obvious to anyone with eyes, of course, completely setting aside his own genius; the physical level of stress, less so.
Edward is the only one who can tell with a touch, able to feel the steady tightness when he brushes an arm against the other, or press a hand flat against the smoothness of his back. There are signs otherwise on the outside, much easier to miss if you aren’t looking--his Ethan is an excellent actor.
With his brilliance comes careful observation; it gets worse when the touch begins, sharp eyes fixing on whatever body part it is, steadily sliding into something calmer some moments later.
The conclusion is obvious from the start, though he does what he can to repeat it, making absolutely certain of his data.
Years of life as a monster isn’t so easy to shake off; with every hint of contact, he’s left suspecting this will be the time Edward’s hand will breach the flesh and disappear inside.
The solution? Simple:
Leaning, holding, the (supposedly) simple things, held out for longer and longer periods of time. With every touch strengthens the layer of knowledge that what he fears just isn’t going to happen.
(And it's...comfortable, touching someone warm like this. He doesn't understand why his own skin buzzes with the touches as well, but he puts it out of his mind. No need to be completely selfish, this time.)
When it graduates to something greater with the single world-shaking event of their lips meeting, well.
Edward supposes it’s a mark of an even greater success than he was aiming for.