Bloodstained guide: How to find secret Demon #44

In order to hit 100% completion in Bloodstained, you need to gather up every item, shard, and locate every demon.

Here's how to find Demon #44, which is one of the most obscure encounters in the entire game.

_{[Spoilers below with the appearance of the monster in image form and how to find it, with one location spoiler.]}