I think it was called Cute Reapers in My House or something similar.
Yeah there is a game called Cute Reapers in My Room but the game im remembering was from like 2015-2016 maybe. Idk I may be getting it confused with something else
It's probably one of the games made by ティッシュはこ studio but I forget it's name.
Oh my gosh yeah thats the person, Tissubox. Wish the games were in english though lol
In my opinion it's hikikomori sister or sloven classmate