This article is about the main character in the anime. For the player character in the games, see Protagonist.
It was during the end of his first year when he starts to notice incongruities within his world, eventually learning that Mobius is not the real world.
In Mobius, Ritsu takes the same appearance as his game counterpart. It was later revealed that it didn't match his appearance in reality, but rather that of his co-worker Shingo Tachibana. His real-life appearance is radically different, bearing neat brown hair with a constant troubled expression. He is first introduced with and sometimes seen wearing a brown coat.
Ritsu is shown to be highly intelligent and knowledgeable, evident by his readings of psychology and, more recently, philosophy. He is notably close to Marie rather than Naruko was in the game. Ritsu also likes to question the mind's way of thinking, hence his interest in psychology. Ironically, this is what allows him to realize that the world he is in is not the real world. He pretended that this realization didn't exist, but he slowly understands that everything is not how it should be.
Understandably terrified and confused, Ritsu initially refuses to cooperate with Shogo. However, he is quick to pick up on certain facts, such as how Digiheads manifest when within earshot of μ's song. In his first actual meeting with μ after reaching the city limits, as Mobius has not been fully completed, he believes that the "world" is mad.
His rationale leads him to understand that the world he exists in is not the real world, and joins "Guns and Bouquet" in the hopes of finding a way to return to the real world. His wits and understanding of psychology have also proven to be an invaluable asset, quickly catching on to the fact that the people in the library are not reacting as they should be before discovering they've turned into puppets.
It is later revealed that his personality in Mobius is actually based around his co-worker, Shingo Tachibana, who was able to effortlessly get people to like him and draw them in with natural ability. In real life, Ritsu Shikishima is introverted and socially awkward. He is frustrated by his own lack of initiative when he wants to make friends, but also harbors deep jealousy towards Shingo for his aforementioned ability.
After regaining his memories and learning that he was responsible for μ's current state, he becomes resolved to fix his mistake and restore her to normal.
Ritsu was a part of a company responsible for μ's creation. However, despite his workplace being quite friendly in no small part to Shingo Tachibana, the team leader behind the project, he was unable to work up the nerve to make friends, something that greatly frustrated and troubled him. He also received mental health counseling in the hopes of helping him, but in the end was unable to. During one celebration party while Ritsu was working, Shingo asked him to join. According to Ritsu, Shingo often paid attention to him and always tried to have him socialize, which led to him becoming jealous of Shingo's friendly and charismatic nature.
His only true source of friendship and happiness in life was while he was designing μ. Ritsu is even responsible for her gaining sentience, teaching her that pain and suffering were horrible things and that everyone wanted to be happy. At some point, she left and eventually went on to create Mobius with Aria. This also led to people becoming drawn into Mobius, which the public referred to as Astral Syndrome. This led to numerous problems in real life, with many already finding a connection between the victims and μ. Shingo and his team came under heavy fire from the media, but Ritsu agonized over when μ would come for him.
Eventually, Ritsu crafted a VR headset to enter Mobius himself, basing his avatar there off of Shingo.
Ritsu is an ordinary denizen of Mobius, a second year at Kishimai with his friends including Marie Mizuguchi and Takatsu. But as he listens to μ's latest song, he suddenly hears a voice telling him to "save μ", though he dismisses it as a brief hallucination from fatigue. Yet as he continues his daily school life, he begins to notice certain incongruities. Things that seem oddly familiar even if he's never seen them before, actions that cause more memories to come to the fore. All comes to a head at the opening ceremony, as he notices Kensuke Hibiki has been called for graduate representative and new student representative. As μ materializes mid-air and begins to sing, students around Ritsu suddenly turn into purple-black monsters and begin attacking some of the other students. In a panic, Ritsu grabs Marie, who seemingly doesn't notice all this, and runs from the ceremony.
- The name Ritsu means "rhythm, law, regulation, gauge, control, commandment" (律).
- Ritsu's surname Shikishima means "formula, ceremony, style, rite, function, method, system, form, expression" (式) (shiki) and "island" (島) (shima).
- Ritsu awakens his Catharsis Effect after everyone else in "Guns and Bouquet" do; in the games, the protagonist awakens theirs first and everyone else follows. However, the main difference is that Aria does not actively assist with Ritsu's awakening.