Mikan Muzou (未完夢像)/theories

Soutarou is Possibly Wanting to Achieve a Goal, but is Feeling Restrained, Guilty, and Scared to Try
This theory is mostly based on the Effects Soutarou uses.

If one uses dream language, the effects (can) relate to feeling restrained, guilty and scared. Some of the effects have a little positive meaning, such as trying to break free from those negative emotions. However, since Soutarou is still stuck in the room and doesn't seem to attempt to be free from those items, it seems he is still struggling to release them. It also seems he is working hard, but he may be just deceiving himself.

As for the environment, it is possible Soutarou is dwelling on past things about the thing(s) that may has/have been hindering him.

Soutarou is Writer with a Creative Crisis
Soutarou can be a writer with a creative crisis. It can be proved by the fact that in the real world, Soutarou has something like a typewriter on a table. Also after collecting all effects, Soutarou gets some kind of book in a dream world, the same book also can be found in a special white room with a bloody dresser. This book can be a work of Soutarou but he can't complete it from the crisis. By the way about the crisis, when Soutarou using the black cat effect crawling through some caves, in the background can be seen some silhouettes on a chair and last of them in the pose of depression, it seems that silhouettes show Soutarou with a creative stupor.

Virus and Salvation
Soutarou's world has been infected by some kind of virus that turns people into hybrids of humans and octopuses, let's call them the Shokushu (from Japanese, it means Tentacles).

It seems that in past, Soutarou had friends before the virus and now these friends are Shokushu mutants, chasers in Soutatou's dreams. Let's call the blonde guy Nate, and another chaser Sumi, who's afraid of becoming like the first one. Soutarou probably called to his friend or maybe girlfriend, the mysterious girl in Gray World(fan name Himemi), and asked her a favor, which until transformation she must finish him off; because Shokushus are not just hybrids but also cannibals. Knowing that Soutarou made himself very weak by jumping off from his balcony, then lying on the ground, waiting for the last strike from dear to end him.

In END 3, Himemi seems to not believe in Soutarou's sickness and she pays by her life. When she comes closer to Soutarou in the last scene, he gets up and kills her. After that, he crawls closer to her dead body and eats her. After one bite, Soutarou makes a growl, and large tentacles grow out from the ground.

Also in the Cave Chaser event, Nate eats Soutarou offscreen, and in the Secret of Manor event Soutarou can find a river of blood and flesh, it can be nothing but food for Shokushu, and they may belong to people, and this may be proved by man-eating nature of Shokushu. Also probably because of that, in books on Soutarou's table and White Room with a bloody dresser, Soutarou could write something like symptoms of his sickness. In True END, Himemi with a club or a bat finishes Soutarou off, giving him salvation.

Reincarnations of Childhood friend in dream
ln his dream world, Soutarou has an unusual NPC; a little girl in the slum, Binbonin. In front of her, Soutarou can't use three gruesome effects - centipede, brass knuckles, and case. Binbonin in truth actually can be Soutarou's friend in childhood, since Soutarou has down jacket effect that makes him younger, and young Sotarou can be seen on the Monochrome Mountain which is inescapable, means that the place is little prison for Soutarou, for what he did something bad to this girl. But also Binbonin can be a mysterious girl in the gray world aka Himemi, but that's not all since Soutarou can turn into the black cat, probably white cat can be another reincarnation of Himemi in a dream world.