Using Yuu as comparison and ammo against Guren is accurate though. Guren just keeps denying it while Yuu is clueless to Shinya and his knowing smiles. Maybe if they had even one adult with them in the aftermath things wouldn't have. Fallen apart quite so much after Nagoya idk. I figure probably prior to canon Yuu likely knows of Shinya because Hiragi fam, and has prob seen or met him around by association with Guren but they hadn't really got much time together before it all.

But yes. Definitely, I feel like there's something to explore with the two of them. Particularly in debating how much Guren has actually confided at least in Shinya and his closest allies on the kid and all around what he knows with the whole seraph experiment regarding the kid even if he. Probably didn't go into certain revelations in recent manga chapters.