Angel's Tale: An Extraordinary Love Story

This is the story of a young man named "Prach" who has a unique ability to see things that others cannot. He lives together with his sister "Fa" during his parents' work trips. The simple life of "Prach" becomes a disaster when strange creatures, that no one can see, show up and try to harm him.

"Prach" must find a way to survive this weird situation. This leads to the discovery of the secret of "Fa", who is actually more than his sister. Not to mention the visit of "Manari", a mysterious girl who claims to be a demon. And her goal is him.

[From Steam]