The character known as "Pico Onedari" lacks distinct existence in official media tied to "Boku no Pico." The term "Onedari" solely references a bonus drama track titled "Pico no Onedari Boisei" ("Piko's Pleading Voice") on the character album "Boku no Pico ~Shota Aidoru Pico Tanjou!~," featuring protagonist Pico without introducing a separate entity.

Pico, a blonde pre-adolescent boy, works summer part-time at his grandfather's beach bar, Bebe. He frequently swims nude or in a blue Speedo. After receiving girls' clothing as a gift from bar regular Tamotsu—who initiated a sexual relationship mistaking Pico for female and continued it upon learning Pico was male—Pico wears the attire. Hurt by Tamotsu viewing him only sexually and refusing commitment, Pico rebels, cutting his hair and fleeing. They reconcile before Tamotsu's absence in later episodes.

The following summer, Pico meets Chico, a younger brunette boy swimming nude in a forest stream. Chico calls Pico "Oniichan" (big brother), and they form a mutual sexual relationship. Though Pico usually adopts a submissive role ("uke"), their dynamic proves reversible. Secretly observing Chico's sister masturbating sparks their own sexual experimentation, and they use her cosplay outfits and sex toys without permission.

Later, Pico and Chico encounter CoCo, a feminine-presenting boy with long black hair and subtle supernatural traits evoking a "city fairy." Pico develops feelings for CoCo, causing tension when he witnesses Chico and CoCo together intimately. The trio reconciles via a threesome atop Tokyo Tower. CoCo primarily assumes the submissive role, though this too can reverse.

Pico evolves from initial naivety and friendship-seeking to navigating complex romantic and sexual bonds. His experiences span emotional conflict, rebellion, reconciliation, and multi-partner relationships across the official OVAs.