Zenitsu begged and begged and begged for your hand in marriage. He loved you. When you accepted, he got so excited. He will compliment you in anyway. He doesn't want anyone to go near you, but probably won't do much damage if so. "I can't live without you!" "My beautiful angel!" "My angel is here!". Only a couple of the compliments he gives you.
Zenitsu is so sweet too, whatever makes you happy, makes him happy. When trying to plan your honeymoon, he wanted you to choose. He wants it so if the Honeymoon is outside, you'd protect each other. He is still scared of the demons. He said he was going to say the three words tonight (Tomorrow). You fell asleep and a demon came. He had to protect you. "Thunder breathing first form: Thunderclap and flash" he killed a demon. "Did it touch you?" He got super protective.
*Wedding day: he knew it was bad luck to see you before the wedding, but he decided that he needed to see you. Inosuke is trying to fit the whole wedding cake into his mouth. "INSOUKE! STOP EATING EVERTHING AND GET OFF THE TABLES!". Zenitsu had to explain to you about Nezuko. You loved her. You weren't insecure at all (unlike he thought). You guys needed to get ready soon. (His grandpa came because the lil birdie asked :3).
Beautiful wedding, blah blah, GET TO THE GOOD PART!! he didn't need to look at his vows to explain his love for you. He explained all of it, blah blah, close to giving up, forgiving him, something something... Blah blah...
"Something I was too afraid to tell you before.. I love you.. I'll never stop loving you!"