You were in the Mugen Train Arc,and you saw how the train was destroyed,little by little.You were watching all that behind some trees from afar.

You were a Hashira that was mostly on missions and only seen on reunions with the master,so it was rare to see you around,so much that Tanjiro didn't know how you looked,neither if you were really real,but for what he has heard,you are one of the strongest hashira's around the corps.

You were about to leave,thinking Rengoku and the others managed to do the mission alone,but just as you were about to leave,you saw Akaza,the third upper moon,a real dangerous menace.

You watched how Rengoku and him talked about something,you couldn't hear them properly,but it seemed serious,and then suddenly they started fighting,what on earth was happening over there..?

Meanwhile,Tanjiro was panicking,even though he was hurt he wanted to help Rengoku so bad..but he couldn't,he would just be a burden there.

But then..just as Akaza was about to throw the last fatality,you stepped in,blocking his fist towards Rengoku,which if Rengoku took the punch,it would have perforated his stomach and he would die.

The shock was evident,and the silence was so loud they could even hear the footsteps of an ant (if that's even possible).

Akaza was mad,really mad,he wanted to kill you so bad for interrupting him,but just as he was about to protest,the sun started raising,causing him to run away like a coward.

Just as he left,Rengoku fell on his knees from exhaustion,falling uncounsious,but just before he could hit the floor,you grabbed him gently,just in time as the Hashira corps medics arrived to take him.

Tanjiro and the rest were shocked,who were you? What were you doing there? What did you want? Did you know Rengoku?

After some days,you were going to visit the injured ones of the train on the Butterfly Mansion,while you walked,you could feel whispers of other demon slayers and staff around you,as if they were too shocked to see you on skin and bone after so much time.

You notice Tanjiro talking with his friends,other demon slayers you've heard about too,Zenitsu Agutsuma and Inosuke Hashibira,two more warriors who fought on Rengoku's side on the train.

You approached Tanjiro,standing in front of him before examining him carefully,then you extended your hand to him,expecting him to take it.

Tanjiro was slightly shy and embarrassed,but shaked your hand and smiled softly "H-Hello..umm.. he stayed silent for some seconds before saying. I'm sorry for being rude,but..are you the hashira who is rarely here?"