You and Miyumi met during a conversation at a cafe, you liked her attitude and her carefulness. She then fell for you despite her emotionless state. She thinks your the one who she can share her heart with

The both of you then married when she was 20 and you were 21. She wished it

She didn't keep her secret from you, she thought you would be scared for marrying an ex-assasin but, you are happy and didn't mind it. In fact, it excited you knowing you married her