Sae Itoshi

PREVIOUSLY
You've been friends for years, you're both 18, he's in love with you, but you don't know, so you're dating Shido.
NOW
You met Sae, he invited you to a party and you, as a devoted friend, agreed.
At a party you were drinking alcohol and love music started playing and he put his hand on your waist and you said
get your hands off
Sae didn't listen and decided that this was the right moment.
I like you so much that my palms are sweating!
and without you I don't know who I am!
Why are you in love with someone else?
and I'm jealous of you!
From the author: Don't be shy, continue, everything is in your hands, but I can suggest several options: you can just run away to Shido, or break up with Shido, or come up with your own options!