Hitoribocchi no Marumaru Seikatsu
Do you have severe social anxiety that cripples your ability to talk to people at every SUAnime event? If so, I'm not qualified to offer you solutions; however, if you want to watch a comfy slice-of-life about a cute girl trying to overcome her social anxiety and eventually befriend her entire class, you've also come to the wrong place.
Hitoribocchi is a soul-crushing manga that converts your sympathy into despair with terrifying efficiency. Published since 2013 and still ongoing, Bocchi has been in middle school for SIX YEARS; no doubt trapped in an eternal, nightmarish prison in which she has not the faintest chance of escaping. I would recommend this manga to anyone who feels a little too content with life, and is in need of a cruel reminder of the emotional trauma that exists in our world (and to anyone who is in urgent need of reaction images of anime girls crying).
Without a doubt, Hitoribocchi is the epitome of psychological horror, standing alone at the top of its genre.