[It's scary and it's new and he's known for a while that Ami likes his brother, but now there's…it's stupid. He knows it's stupid to feel like it's a threat but their world's always been pretty small. Hiro's world, at least. It's always been Tadashi and it's always been Cass. He hadn't even met Tadashi's friends from the lab until recently, so the idea of Tadashi having a girlfriend…someone to dedicate other affection and time toward. It's…weird.

He's staring him dead in the eye though and almost-pouting.]

…you lied to me. You said you were with Levi when we were talking about Katsura but you were with Ami instead, weren't you? [He remembers that split hesitation, bro. Even that aside how was it possible he completely missed that? He knew Tadashi wasn't home as much some days but he assumed it was work or ViViD or something dumb. Some of those days when he's by himself in their apartment he seeks out Ruby, but he still had to wonder where Tadashi was. Now he knows. Now it all makes sense.]