After the final fight with Muzan, Sanemi and Giyuu use their remaining time to live by befriending each other and living out their shortened lives. Sanemi gets a bit attached to Giyuu and falls in love. However, Sanemi is late for his confession and Giyuu dies by the demon slayer curse mark on his birthday. They both reincarnate and meet in odd circumstances 100 years in the future. 👍🏻