Majiru Itoshiki is the nephew of Nozomu Itoshiki and the son of Enishi, the eldest brother of the Itoshiki family. Abandoned by his parents, he was sent to live with Nozomu, becoming a permanent resident in his uncle's household. This familial disruption is reflected in his name; the kanji for "Itoshiki Majiru" (糸色 交) compress horizontally to form "zekkō" (絶交), meaning "breach in a relationship."

He presents as somewhat arrogant for his age but frequently endures psychological trauma from the erratic behaviors of Nozomu's students, a recurring source of comedic distress. Majiru dons traditional Japanese attire, specifically a kimono and hakama, mirroring his uncle's typical wardrobe.

His closest bond among the students is with Kiri Komori, the class hikikomori. He spends significant time in her room, with subtle narrative hints suggesting he harbors a precocious crush on her. This dynamic highlights his vulnerability and search for stability amidst chaotic surroundings. Majiru's existence within Nozomu's home frames him as a "pretty freeloader"—a dependent reliant on his uncle's strained hospitality without contributing domestically, emphasizing his status as an unintended ward.

No official media depicts substantial character development or major story arcs centered on Majiru beyond these established traits and situational interactions. His role remains consistent as a secondary character whose presence amplifies the absurdist tone through his reactions to others' quirks rather than personal evolution.