Shiki Ittensai

* * *
About fifty years ago, Nagame met a certain talented psychic in Japan. The two quickly fell in love, and Nagame —who by that point had begun to earnestly wish that she could give up being a mermaid and live among humans in the mortal world— asked him whether there was any way she could become human. Wanting to fulfill her wish, the psychic began to search for a lost secret art that would allow her to assume human form. The two overcame countless hardships together in their quest for the art, and after decades of searching, they not only found it but finally succeeded in perfecting it.
However, the secret art that would grant Nagame her wish demanded a heavy price: for a mermaid —a being who lacked a mortal form in the material world— to gain a human body, the caster's own body would have to be sacrificed. Using this art would render them unable to live side-by-side as humans as they had so longed to do.
The two agonized over their decision. Despite their decades-long search, the different worlds in which they lived continued to keep them apart —as a mermaid, Nagame could neither join him on land nor appear before others. The life together they yearned for remained a distant dream.
In the end, the two chose to use the secret art so they could be together in the mortal world. Even when Nagame learned that the psychic, Ittensai Shiki, only appeared young due to his supernatural abilities —having been born in the Edo period and already over a hundred years old by that time— she loved him no less.
* * *
After many twists and turns in their quest for happiness, the spirit of Ittensai Shiki, who sacrificed his body so that Yumeko could live as a human, has come to dwell in the body of a small dog, and he continues to enjoy retirement and a quiet life at Yumeko's side in his home in Tokyo to this day.
Even before his retirement (and despite his current form), he remained an active force in the industry, having devoted his time to such things as taking Sodo Kiryu on as his protégé after discovering his potential, assisting with management of the Paranormal Affairs Bureau for old times' sake, and sending Yumeko —who knew of the Bureau and the work it did— to help out as one of its members.