Shu Inuzuka attends high school, progressing from Class 2-4 to Class 3-3. He sports spiky blonde hair, orange eyes, a slender frame, and fair skin. His signature look features the school uniform worn without a tie, gray pants, and white sneakers. Friends frequently call him "Inu" (dog), a nickname he consistently asks them to replace with his full name.

Outwardly happy-go-lucky, Shu harbors a strong sense of responsibility, especially towards his best friend, Yuu Izumi. He actively shields Izumi from frequent accidents, physically intervening even at risk of personal injury. Beneath his carefree exterior lies a diligent work ethic; he juggles multiple part-time jobs to fund his dream of becoming a veterinarian. This goal requires university attendance in another region, a prospect causing him significant anxiety about leaving his friends. Fear of their reaction keeps this plan undisclosed.

Shu boasts athleticism, participating actively in sports alongside peers like Miyako Shikimori. However, his abilities have limits—he sometimes loses competitions or fails to fully protect Izumi. His character evolves from initial self-focus to prioritizing his friends' emotions and well-being, a change fueled by deepening group bonds.

His relationships are central. He shares a profoundly close and trusting friendship with Izumi, spending extensive time together and earning Izumi's explicit "best friend" label. This bond occasionally sparks jealousy in Shikimori, though Shu remains dedicated to Izumi's safety regardless. Interactions with Shikimori's friends, Kyou Nekozaki and Yui Hachimitsu, involve playful teasing about his nickname. At his coffee shop job, he admires colleague Rika Isana, who respects his determination and work ethic in return.