It takes Pietro a while to put things together, sometimes. A very long while, when you consider how quickly he observes the details he fails to connect, but social awareness isn't his forté, and Cassian's knack for discretion doesn't help. But Pietro doesn't miss the fact that Jyn is over at Cassian's house before him from time to time, or hanging around Go Ask Alice, or that more often Cassian can be found heading over to 4106, which Pietro eventually notices is Jyn's house. Not only in the afternoons or evenings after work, either; he notices Cassian come down the street from that direction once in the early hours of the morning, and he's not an idiot. He's quite good at jumping to conclusions, thank you.

But he doesn't know much about Jyn. His policing of his siblings' social lives has a patriarchal bent neither of his sisters probably appreciate very much, but Cassian is not entirely exempt — it's just that he doesn't remember Jyn being around town for long, and there's been insufficient gossip. He'll have to find out himself. And soon, if they're going to be spending that much time together.

So the next time he sees her out running through the neighborhood, he shows up alongside her. Just falls into step, easy as can be. It seemed less rude to him, somehow, than showing up at her house uninvited.

"What are your intentions with my brother?"

Proper introductions, it seems, are not part of the plan. He's not that concerned about his manners.