An omnibus collection of interconnected short stories by Douman Seiman.
Melancholia is a completed manga by Dowman Sayman, first published in 2017. It blends sci-fi, historical, psychological and romance. You can read all 27 available chapters of Melancholia online for free on MangaPulse; the newest is Chapter 26, added 2019-04-06. The series is finished, so you can read it from start to end in one go.