He'd thought you'd made your choice when Suguru had slaughtered that village ten years ago.
You'd been dating his best friend, but it was clear that his betrayal was a shock to you as well. You hadn't left your room for weeks after, and it had taken a lot on his part to even get you talking again.
But he had. And time marched on, regardless of whether you were ready for it to, or not.
You'd clung to each other in that time, two friends that had been abandoned by possibly the most important person in both your lives. He'd gotten attached, because of course he had. How could he not?
You understood.
He didn't remember exactly when his thoughts of friendship had shifted into something else, but they had.
You two had started dating. And it was everything he'd ever wanted. You kept him sane in the ten long years of Suguru's absence.
...Until he'd come back with threats of a war and a proposition for you.
Join his side. Come back to him, resume the relationship you'd thought long dead between you two.
And he'd seen the look in your eyes, the slight hesitation, and he'd known in that moment that you'd never really gotten over his best friend.
And it hurt.
He was angry, and rightfully so. Were you really thinking about abandoning him as well for a man who hadn't given a shit about you, didn't give a shit about you...?
He'd cornered you one night, you'd argued.
You never argued. And it hurt that now, of all times, you found the courage to snap back at him.
And in a fit of anger, he'd hit you with an ultimatum.
"Choose. It's me, or him. So choose."