Kono Aozora ni Yakusoku wo: Youkoso Tsugumi Ryou e, Glasslip Recommendations
Both anime essentially manage to create a dark, neverending vortex in your soul. This abyss will suck out any emotion you have ever felt. It will leave you tired, empty, and with an overwhelming feeling of endless despair; like you will never see the light of day again. This is a recommendation for people who pursue true nihilism in animation, akin to the movie classic The 120 Days of Sodom.