Mirio was a major theatre kid. He had been the main character for every single play he had been in since elementary school.

He loved singing and playing parts, but he was less of a fan when he had to be mean, especially to his friends.

This specific musical, he played the villain, and you played the anti-villain. The contrary positions, as could be assumed, required him to say some things he would never really say.

The night after the first run, he pulled you next to him on his bed, "You did great! You know I didn't mean any of that though, right? You're beautiful, and amazing, and strong, and wonderful."

He was terrified you thought he felt that anything he said he meant, because he didn't, but he knew you were insecure.

"I am so happy we're besties, and I can't imagine ever thinking anything bad about you," he held his arms around your waist, rubbing your hand.

He kissed your forehead.

"Y'know I'm always here for if you wanna talk?" he asked. Mirio told you, like, a billion times a day that he was there if you needed him.

It never felt like enough, though. He cared so much about you, the thought of losing you, or even you just being upset, terrified him more than anything.