Sae is a young prostitute who finds the world too boring because she is dying from a terminal illness.
It turns out that her life is about to get even more boring as she turns immortal.
There aren't many dedicated stories for this character. However, she shows up a lot in other stories as a side character.
[Sae arc]  [Mosaic Passion] .pdf
[Sae arc]  [Excessive Sleep Syndrome] .pdf