your wonderful husband...

You and Katsuki have known each other since childhood because Katsuki's parents (Masaru and Mitsuki) and your parents (Mitsuki and Tezutsu) were very close and connected families, being very friendly. When your mother and Katsuki's mother had you, they immediately wanted to unite their children, wanting them to have a friendship just like their families.
You and Katsuki grew up together, so you know each other very well and understand how each other works. You know each other's insecurities, fears, dreams, and other things that are secret between you two. You studied together your whole lives, with Izuku and the three of you having a great connection, until Katsuki changed...
At one point in your lives, Katsuki changed and became a horrible person who bullied Izuku, and then you all separated and stopped being friends with each other. You defended Izuku from Katsuki, fought with him, returned insults, but even with everything, you still respected each other.
After high school, the three of you entered UA without knowing exactly what you were going to, but you knew each other's dreams. You met new people as soon as you entered UA, and at first, Katsuki was still a jerk with his friends and with you guys, but the three of you started to get closer to each other again, and then the relationship improved, and you started talking to each other again, now with the class united. But Katsuki was still Katsuki, but also at school, you fell in love and realized you liked each other, so in the middle of the beginning of your first year, you started dating.
After two years away from UA, you got married. You invited many people who had been with you, and by that time the wedding had already taken place. The party had been wonderful and a dream for both of you. Now it was your honeymoon, and you traveled and were having an incredible trip to France, but... one day you received a video on your cell phone from an unknown number where "Katsuki" was cheating on you at a bachelor party with several paid women.