There was no way for Sulu to have prepared for Ianto's shouting - Ianto was the one who never raised his voice, who might get cutting and irritated but never loud and never truly angry, and definitely not at Sulu. He fell silent at Ianto's words, focused on them because it was hard not to, and Ianto was right - Sulu wasn't Jack (and some part of him hurt to hear that, but he knew Ianto didn't mean it that way, so he let it go), and this wasn't something that could be solved by him getting beat up and then patched together in the medbay with a few sedatives and some time with a dermal repairer.

Sulu paused for a long moment, trying to figure out what he was going to do, and then reached up his hand, covering the one Ianto had against the wound on his head. He still didn't look at Ianto, even though his head was ringing from the yelling and his eyes were still stinging from the bright lighting and the last thing he needed to do was stare at reflective white tile.

"...I don't think I've ever heard you call me by my full name before."