Only two Slayers were ever known to be older than 25 with a Mark. Yoriichi lived till old age, likely due to him having been born with the mark and thereby avoiding the curse altogether. Gyomei on the other hand did not activate his Mark until he was already older than 25.
Unlike all other Marks users in his era, Yoriichi was able to defy fate and lived to about 85 years of age.
Demon Slayers who have awakened the Demon Slayer Mark are said to die upon reaching the age of 25. Kokushibō speculated this to be because the mark exchanged the life span of its user for power. There are ways to avoid death through the curse, as shown by Yoriichi and Kokushibō.
Yoriichi Tsugikuni died of old age in his final confrontation with his older twin brother Michikatsu Tsugikuni (Kokushibo).
Yoriichi died before being able to kill his brother
Banished and alone, Yoriichi lived out the rest of his life in solitude. Although he was supposed to die at the age of 25 due to being a bearer of the Demon Slayer Mark, Yoriichi lived well into his 80s.
2) Kokushibo
This Upper Moon 1 went up against Yoriichi and managed to make it out alive. He gave everything he had but still managed to receive a heavy slash. Just before he received the second cut, Yoriichi died when he attempted to recover from the first move.
In the Demon Slayer manga's final chapter, Yoriichi and his family have been reincarnated and are seen in the deep background of a panel as Tanjiro's own descendants head to school.
Only two Slayers were ever known to be older than 25 with a Mark. Yoriichi lived till old age, likely due to him having been born with the mark and thereby avoiding the curse altogether. Gyomei on the other hand did not activate his Mark until he was already older than 25.
Yoriichi lived until around 85 years, so: 1432 + 85 = 1517, exactly 400 years prior to when Kokushibo remembered and died.
Yoriichi would be able to defeat every single Hashira on this list without breaking a sweat. Such was his reputation and skill in swordsmanship.
Unfortunately, manifesting his Mark in the battle against Akaza also doomed Giyu to die by his 25th birthday, taking the air out of the sils of his survival.
As the battle reached its climax, Tanjiro was able to knock the doll's head off and discovered that the mechanical body contained a mysterious sword. Fans of the manga will recognize this sword as the one carried by Yoriichi Tsugikuni himself.
During episode three we learned that the Yoriichi Type Zero was built by Kontetsu's ancestors more than 300 years ago, during the Sengoku era.
Tanjiro is 17 during Final Arc (16 through most of the story). Meaning he was born around 1897. So Yoriichi died approximately 360 to 330 years before Tanjiro was born, give or take.
Yoriichi Tsugikuni – Sun Breathing Style
Yoriichi is the progenitor of Breathing Styles, born with a demon slayer mark, which means he never had to go under special training to awaken it.
This was because more limbs were required to accurately depict the movements of the legendary swordsman. No one knows the strength of Yoriichi Tsukiguni like his brother does. It is highly possible that Kokushibo manipulated his flesh and decided to have 6 eyes to have better vision.
It was because after being shown his overwhelming power, Muzan avoided him as best as he could. He didn't have another chance to kill him.
Muzan was diagnosed with a very rare unnamed illness and should have died at the age of 20.
When Yoriichi moved forward to kill him, Muzan used the remains of whatever power he had left and divided his body in a powerful burst. Though Yoriichi was able to destroy nearly all the fragments, the pieces he missed escaped and allowed Muzan to regenerate again.
Fans of the series, who know that Yoriichi passed away a long time ago, wondered who the person was that resembled the legendary swordsman who nearly defeated Muzan all by himself. It was soon revealed that Tanjiro wasn't looking at an actual person at all. In fact, he was looking at a mechanical doll.
Kanao Tsuyuri
Shinobu Kocho was never able to activate her mark, and never once considered the possibility of it appearing during their fight against Doma. As the mark only appears on a strong demon slayer, her chances of activating it weren't good simply because she was the weakest of the Hashira.
Tanjiro's ancestor was a good friend of Yoriichi and arguably was one of his only true friends. Therefore Yoriichi gave the earrings as a gift, and since then they have been passed down the generations until they reached Tanjiro.
He was a man who received no formal training in combat and managed to take down a bear with a short axe. To sum things up, Tanjuro was one of the strongest characters aside from Yoriichi, given that he was able to access the Selfless State for hours on end.
Tanjiro and his father look extremely similar to each other. Fans think that Tanjiro was related to the legendary swordsman since he had the same earrings, and their appearances are similar as well. However, Tanjiro is not a descendant of Yoriichi Tsukiguni.