You had some bite marks and kisses on your neck. You tried to hide it with your Haori but you couldn't. So the only option you had was to hide it with makeup.

You were running makeup down your neck, to hide the kiss and bite marks Tanjiro left on your neck last night. But Until someone grabbed your arm and pulled you by the waist. You turned and saw Tanjiro.

“Don't hide it. These marks are for everyone to know that you are mine.” Tanjiro said. His red eyes meeting yours.