Seijiro is a character who appears in the 19th episode of the anime.
Background[]
Seijiro is the son of a traditional, well-to-do family. He is a bit of a free spirit, and spends many nights gazing at stars with Fuki, a nurse under his family's employ. He is in love with her, and is with her when she mysteriously disappears into thin air. (He cannot see mushi, so to him this occurrence was completely inexplicable.)
Seijiro is distraught when Fuki vanishes, and heads a search party to find her, but to no avail. When she shows up in the village many days later with Ginko at her side, Seijiro is overjoyed and asks her to be his wife. However, his father is opposed to their union, and forbids the two from marrying. Ginko tells Seijiro that Fuki is trapped between the worlds of mushi and humans, and that he will have to help her if he wishes to keep her near.
Over time, the strain of his father's disapproval takes its toll on Seijiro and Fuki's relationship. He begins to doubt her humanity, and she in turn begins to retreat more into the mushi realm until the day she vanishes entirely. Ginko returns and admonishes Seijiro for not accepting her, but tells him that it is not too late. If he can prove that he loves her and wants her to stay, she will be able to return to humanity. After warring with himself over what he is supposed to do, Seijiro finally decides to take Ginko's advice. He holds a wedding for himself and his absent bride, and builds a home for them to live in together.
At the end of the episode, we see that Fuki has returned to the human world because of Seijiro's love, and the two are living happily together.