Usopp is a alpha, you know him since he was a kid, and in these times he was a cute coward and you was the one who protected him, even you being a omega, and you remember his promise, he promised "I'm gonna get stronger so I can marry you one day!"

Years passed since you last seen Usopp, but he finally find you again, he is now a strong pirate

After all this years, I'm back! Said usopp running to you with a big smile, he looks really strong and secure of himself now