Together, atlas. | Sanegiyuu & Manga Spoilers.
noobwoob
Sanemi and Giyuu are together after the battle with Muzan. Finally, being friends, finally confessing their feelings. Finally, being together. Finally, being at peace. The only downside is they lost friends, family and comrades which cannot be replaced. Unfortunately, they don't have much longer to live themselves. Obtaining the demon slayer mark during the battles to the death caused them to only have 3 years left to live. You die at age 25 when you obtain the demon slayer mark. Sanemi and Giyuu are 21.
Once again, this includes spoilers for Demon Slayer, so if you're anime ONLY please DO NOT read this. There are HEAVY spoilers especially in the first 3 chapters.