Giyuu is the water hashira, shinobu is the insect hashira, sanemi us the wind hashira, gyomei us the stone hashira, uzui us the sound hashira, rengoku is the flame hashira, muichiro is the mist hashira, mitsuri is the love hashira, obanai is the serpent hashira, and genya isn't a hashira he is just sanemis younger brother and has beast breathing which allows him to be a demon by eating demons. And btw hashiras are the strongest swordsmrn who kill demons.