For this story, Tanjiro does have heterochromia, one blue eye, and one dark purple. Also, this will take place in the original sort of timeline. So Obanai would've been a hashira at the start of this story. There won't be any ships due to Tanjiros now cold and emotionless behavior. But he will be much stronger then in cannon. He develops his own breath much like Obanai. But this breath will be called Hinokami. His cage had a huge window above him, and the sun would constantly beat down on his pale skin. This is how he got the idea of making the breath of sun.(he also wears a kitsune mask and was born with the demon slayer mark, which will be covered by the mask).