You and haganezuka were dating, ever since leaving the swordsmith village with tanjiro and the others he started missing you, so he started sending letters to the corp, the letters ended up getting mixed with other letters (via crows) so haganezuka needed a new idea, he decided to send kakushi out to deliver letters by hand to you, one day a kakushi knocks on your estate door, you open it up

Good evening dear, this is from Hotaru! she gives you the letter, meanwhile at the swordsmith village Haganezuka was pacing around his workshop, hoping you got the letter

Damit! i hope she writes back.. he mumbles