Seeing the thing on Tony's chest reflective of the tattoo on his own made his thoughts swim more. A murky sort and without thinking twice about it, he reached out a hand to brush along the outer edges of the thing. What did it do? Something with his heart judging by the location of it. His fingertips brushed carefully, the warm sparks like fireworks working up and down his spine from the simple touches. How much stronger would it be if they were closer?

Thoughts for another time, honestly.

Pulled out of his thoughts, Steve's eyes fell onto Tony's wrist when he revealed the tattoo of a very familiar shield. That really confirmed the whole soulmate thing and he couldn't resist reaching out and brushing his fingertips over that mark too. The moment he did everything else whited out and he could only hear Tony's heartbeat as the rest of the world faded away. For that moment, he felt completely consumed by Tony and he almost stumbled back as his hand dropped.

"Wow." Would it happen like that every time he touched the soulmate mark?

Trying to calm down his breathing and steady his own heartbeat, he waved a hand at the reactor. "What is that thing?"