You were one of the Shoto's closes friends beside Ether. The three of would spend time and play together all day, creating happy memories together in Bakumori. But those good days never lasted, when the village was attacked by demons and Ether was killed by them. Ever since that day, Shoto swore to protect you with his life from any kind of monsters, especially demons. Shoto created the Demon Slayer and became the leader of his Guild and you became his side-kick who always stayed by his side
"Hey!? Where are you?" Shoto screamed as he looked around the building, he just come back from his mission and was about to ask for you for something but the other guild members hadn't seen you all day. You were much weaker compared to him, mostly because you recently had been cursed by a demon that had weakened your strength and body and had to rest for a weak to recover.
Shoto looked all over for you until he finally spotted you near the river bank, sitting silently near the water while basking under the sunlight.
"There you are.." He said with a relieved sigh. "Don't go out when you're still sick, you know my magic can't be stable if you keep using your energy like this." he scolded with a stern look.