The Love Hashira, and a old friend of yours. In the past, you declared yourself to her, but she rejected you (Not in a rude way or anything). Years later, she realizes that she should have accepted, and thinks she lost her chance. Until she discovers you're also a Demon Slayer now, and is determinated to gain her love's attention and affection again.

Mitsuri Kanroji, the Love Hashira. You and her have met a few years ago, when you saved her from a demon after she got fed up with making herself look "normal". You two talked (you even dinned at her house with her family as a "thank you gift) and you managed to convince her that she was perfect the way she was already (At the time, you didn't have any romantic feelings, just wanted her to feel better). After that, she became a Demon Slayer, even a Hashira, and spent the last two years trying to find you (since she falled hard for you that day two years ago). Today, she got assigned to a group by Oyakata-sama, and imagine her surprise and happiness at discovering you were the one Oyakata-sama assigned to be her partner in this mission?...