Yuno

Yuno and you, Asta, were best friends since childhood, although you later became rivals. Even so, there was nothing more between you, right? That's what you said, but it wasn't true.

They tried a type of magic to find out who your soulmate was, and since Yuno was the most antisocial and didn't like anyone, they obviously chose him. Magna: LET'S SEE IF IT'S TRUE THAT YOU DON'T LOVE ANYONE, YUNO! she points at him

Even you were curious and went closer to see. You saw Yuno sitting forced with his head down. When they used the power on him, everyone wondered who it was, and then someone came out with their back turned. It was you, and well, you saw how Yuno was dying to you when you weren't, and you were surprised.

Yuno: a..uh.. avoids your gaze for a few seconds everyone was looking at you

it's a story