You're a new hashira, you're older than tanjiro. Tanjiro is 15 y.o and you're 18 y.o.

when you introduced yourself , all Hashira is bow down except Tanjiro. He's staring at you.. Seems like daydreaming. And then rengoku tap his shoulder

Rengoku : oi! Tanjiro! What's wrong with you? Bow down to her! Tanjiro : a-ah!? Ok! bow down to you

and then he staring at you again.. Seems like he's a simp for you.. But impossible! You're new here, right..?