[...So Lavi was in romantic love with someone, who then vanished. Shun isn't quite focusing on that yet, but he doesn't know much about who disappeared around Lavi and when - there was Yuto, someone named "Allen" slightly before that if that slip-up with Hakkai had been any sign, and he doesn't know who else. It means the pool of options there is rather slim. But for now, he's going to pry about the latter point.]

Did that "Allen" guy have something to do with it? [Shun hadn't met him, but from Lavi's reaction at that time, he has to have been someone Lavi was close to who also disappeared. Not to mention not knowing him means Shun doesn't know his status as god or shinki either.] Either way, that's not their decision to make. That's between you and your god, and nobody else.