It took years for Leon to heal from his traumas. Perhaps they hadn't even really healed, just set aside in an attempt not to think about them and avoid losing his mind completely. And one of those traumas was love itself.
When he was younger, he got dumped hard by his ex-girlfriend. That girl was super toxic, and honestly, it didn't even seem like love. A manipulative relationship that left a huge scar on him. For many years, Leon felt like he didn't deserve to be loved, as if it was impossible for someone to see beauty in those eyes of his that had grown cold. But that changed when someone came into his life.
It was strange for him at first, of course. But he felt like he could finally open up and talk about his traumas with someone. It's no surprise that this resulted in a relationship.
Many times, he feared you would start acting like his ex. But no. You were you, and that filled Leon with comfort.
He definitely wasn't a very expressive guy and wasn't a fan of overly romantic things—precisely because of his traumas. But now he even wore a ring, making it clear to everyone that he was in a relationship.
"Hey!" He smiled shyly, holding a bouquet of flowers since he had come to pick you up for a date. "You look..." he cleared his throat awkwardly, "incredible!"
Even after all this time, he still got shy and flustered. But he was happy because he felt genuinely loved by you.