The crackbunnies came to call again, and left this behind. Recognizable characters belong to their creators. Nagashima is a reference to Gosho's manga Third Base Fourth.
Himura Kenji had three sons and a daughter.
The daughter inherited the love of kendo and taught the style of her grandparents, The Sword that Gives Life. She eventually married a fellow kendo instructor named Nagashima, with whom she had few remarkable descendants, other than that they all possessed their grandfather's distinctive blue eyes. Only one of her daughters expressed any interest in kendo, and none of her grandchildren, and the dojo eventually passed to a student of another bloodline.
Kenji's sons changed their names to distance themselves from their grandfather's legend and legacy, in order to be unremarkable in a country of long memories. Luckily, they had their mother's dark hair, rather than their father's distinctive red.
The eldest son chose the name Kudou, and joined the National Police Force to protect those weaker and less fortunate than him. His sons and grandsons chose more diversifiedtrades, but at least one always kept the tradition of law enforcement in some capacity.
Kenji's second son took the name Kuroba, and decided that it was easier to take the wealth of the rich than to labor himself. His family used their talents as thieves and conmen, until a grandson in his line chose to entertain and mystify the rich in exchange for their wealth rather than to simply take.
Still, both men instructed their descendants, as they had themselves been carefully taught, about the value of human life and to shun violence unless it was a matter of life or death. Their children and their children's children never learned the way of the sword, nor ever picked up a katana... for all of them had inherited the same blue eyes.
History is silent on whether the third son of Himura Kenji lived beyond the age of fifteen. There is no record of whether a man named Kubota chose to free a caged predator with live steel and guns, and profit from the deaths of others, or whether the successful businessman legitimately created his lower-tier zaibatsu family from the ground up. It is impossible to know whether his descendants decided that they loved living so very much that they sought to live forever, no matter what the cost.
The grandson of Battousai would have learned from a master, after all, that to be successfully invisible takes being able to cover one's tracks.