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 in a 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 creative crisis, its can be proved by a fact that in real world Soutarou have a something like a typewriter on a table, also after collecting of all effects Soutarou get a some kind of book in dream world, same book also can be found in special white room with a bloody dresser, this book can be a work of Soutarou, but he can't complete it from the crisis, btw about crisis, when Soutarou usin black cat effect crawling through some cave, on a background can be seen some silhouets on a chair and last of them in pose of depression, it seems that silhouets shows Soutarou with a creative stupor.

Virus and Salvation
World of Soutarou infected by some kind of virus, virus that turn people in hybrid of human and octopus, let's call them Shokushu, from Japanese means Tentacles, it seems in past Soutarou had friends before virus and now this friends is Shokushu mutants, chasers in Soutatou dreams, blonde guy fan name Nate and brunette guy fan name Kuroji, afraid to become like them Soutarou probably call to his friend or maybe girlfriend, mystery girl in Gray World, fan name Megami, and asked her a favor, until transformation she must finish him off, because Shokushu not just hybrids, they also cannibals, knowing that Soutarou make himself very weak by jumping from his balcony, then lying on the ground he waiting last strike from dear to him person, in END 3 Megami seems to not believe in Soutarou's sickness and she pay by her life, when comes closer to Soutarou last one get up and killing her, after that he crawl closer to her dead body and eat her, after one bite, Soutarou make a growl and from the ground break out a big tentacles, that belongs to Soutarou, also in Cave Chaser event, Nate eat Soutarou offscreen and in Secret of Manor event Soutarou can find a bloody and flesh river, its can be nothing but food for Shokushu, and this bllood and flesh belongs to people, and this proved man-eating nature of Shokushu, also probably that in books on Soutarou's table and White Room with a bloody dresser Soutarou can write something like the simptoms of his sickness, in True END Megami with a club or a bat finish Soutarou off, giving him a salvation.

Reincarnations of Childhood friend in dream
In his dream world Soutarou have unusual NPC, a little girl in slum, Mazushi, in front of her Soutarou can't use three gruesome effects, centipede, brass knuckles and case, Mazushi in truth actually can be a Soutarou's friend in childhood, since Soutarou have effect of down jacket that makes him a young boy, and young Sotarou can be seen on the monochrome mountain and this place inescapable, means that little prison for Soutarou, for what he did something bad to this girl, but also Mazushi can be mysterious girl in gray world aka Megami, but and that's not all, since Soutarou can turn in black cat, probably white cat can be another reincarnation of Megami in dream world.