Yoriichi try the same younger dual of Kokushibo – Michikatsu in such a case as this is title you to definitely Yoriichi knew him given that. During their childhood, Michikatsu constantly looked at Yoriichi since inferior to him. In the event that twins was indeed produced, Yoriichi is actually ostracized from their sibling because of the grotesque mark he bore, while Michikatsu are selected to get the latest replacement of your household members. He pitied Yoriichi for what he regarded as childish choices, spurred on the by the how Yoriichi manage cling on their mom. Regardless of this, Michikatsu went out of his way to correspond with and interact with his young brother, also risking beatings using their dad exactly who forbade interactions involving the a couple. On one event, Michikatsu snuck in and you can provided Yoriichi a home made flute. He informed him to spend inside and in case he had been within the problems, proclaiming that he would been straight away to safeguard his younger sis. 
Michikatsu try disturbed of the his brother’s smile and you can unclear about his brother’s cherishing regarding exactly what the guy said to be a “bit of rubbish”
Whenever Yoriichi try shown to have a prodigious, Tiere Dating sheer ability having swordsmanship, the brothers’ opportunities into the home were stopped. Michikatsu is no further said to be the successor of one’s members of the family, taking up his brother’s small, separated area if you find yourself Yoriichi got their lay once the family’s heir. So it skills fueled Michikatsu’s desire to grasp the methods of your own sword and you may perform stoke brand new preparing thoughts of envy with the their brother.
As he told you his goodbyes, Yoriichi brought out the newest flute Michikatsu got made available to him
Whenever its mom died unexpectedly, Yoriichi advised Michikatsu which he might possibly be leaving family. He smiled, carrying it close, telling Michikatsu it was dear and that he concept of it as your. After learning its mom’s log, Michikatsu discovered that Yoriichi wasn’t holding in order to his mom however, was basically support their, which have known about how her disease weak her. That it summary infuriates Michikatsu, an intense hatred and jealousy towards Yoriichi bringing root within this your, to the level where he wants Yoriichi got never been born and mentally pleads having him so you can pass away. 
Which disliked merely expanded as he is stored off a devil of the Yoriichi himself, who’d be more effective. Immediately after leaving his members of the family, the guy joined brand new Demon Slayer Corps to fight next to their aunt and be stronger. Michikatsu themselves attempted to understand Yoriichi’s Sunshine Breathing but is actually not able so you can, alternatively having fun with a good derivation you to definitely turned into known as Moon Breathing. Michikatsu after that turns to your a devil as a result of Muzan just after lamenting their failure in order to previously exceed Yoriichi in electricity. 60 years later, both do satisfy the past day. Michikatsu are unnerved because of the Yoriichi’s mourning out-of their choice, but are still terrified up on enjoying your prepared to attack. Whenever Yoriichi hit, Kokushibo is actually too sluggish to respond and you will is nearly beheaded. Looking forward to next hit, he know Yoriichi had passed away out of retirement and angrily cut their human anatomy on feeling of inferiority he attained while in the their lifestyle.
This is greatly designed by tears forgotten by the your immediately after with the knowledge that brand new flute he’d talented his sibling got stayed which have Yorichii anyway this time around. In turn, Michikatsu couldn’t spend the new flute following latter’s passing, and leftover they toward his individual for hundreds of years after that up until his personal dying. At some point, in his latest minutes, he understands their aunt are past your in most ways and you may questioned your having why he was even created.