Alex is most likely an older teenager/young adult and is usually drawn older than most dreamers, with mid-length black hair parted in the middle and a blue shirt with a four-checkered light and dark blue design on the front of it with dark blue long sleeves. Like Madotsuki of the original Yume Nikki, his eyes always appear to be closed.
Alex is likely a somewhat isolated individual who does not feel accepted by people. Unlike in a lot of fangames and in the original Yume Nikki itself, he is able to leave his one-roomed house and travel in the foggy street outside. His actions reveal him to be an unmotivated but imaginative individual on his own terms. For example, while he is uninterested in reading books after his computer -- the tool that likely served as his creative conduit, perhaps in another allusion to .flow -- has shut down and he's tried a few, his dream world shows Alex's outlook towards use of color and neutral shades and evidence his interest in nature.
Worlds that are populated by natural elements, such as Sky or Forest World, tend to be empty, relaxing, and unrestricted to the protagonist. The few individuals that live there, if any, tend to be peaceful. On the other hand, characters located in more crowded, urbanized areas are more malevolent or indifferent towards him, whether they be chasers or simply NPCs that opt for monophonic sounds upon interaction over actual spoken dialogue that other, more friendly characters may avail themselves to. Some exclude him when he tries to join in a group: the green block with a martini in Color World 3 says "the party is over" and nothing else, despite the fact that two other socialites are in the room and no efforts are being made to end any sort of social gathering -- in fact, the block itself seems quite settled.
In another example, the first girl you encounter in the black and white mask area says, "This place is too good for you. Get out." She is smiling and continues to walk around. The fact that this all occurs in the dream world of an individual who lives alone indicates that this could be a result of his current self-image in terms of how he believes others perceive him or traumatic social incidents that may have occurred in the past, staying true to the nature of Yume Nikki and its derivative games.
One notable exception to this peer-rejection pattern seems to be the Shopkeeper, who on first appearance is very friendly towards Alex, even going so far as to give him a free effect to coax him into becoming the "buying type." However, his sincerity of goodwill towards the protagonist is arguable -- after the initial conversation, the only thing the man says is, "Welcome!" before taking the player to the shop screen, likely indicating that once his ulterior motives, i.e. convincing Alex that he is an approachable individual worthy of a loyal customer, have been realized, he is comfortable with resigning to his true hidden personality of indifference towards any personal struggles of the main character; perhaps the fact the bangs of his green hair cover his eyes and his ever-present smile are symbols of this untrustworthy characteristic. Interestingly enough, the effect you receive from him is Protagonist.
It's possibly that Alex has issues with his view of his art skill level, or has been unable to find work after school/possibly dropping out of school.