Sai

Sai is a thickset man sporting shaggy brown hair along with sideburns. His torso is oddly smooth and tube-like, and for all his muscle he shows neither defined abs nor a navel. He wears a dark green cape topped by a white frilled collar, puffy blue-and-yellow striped pants, and black shoes, and the number "13" is inked on his left side below the ribs, echoing his grandfather's "12" and marking him as the Happo Navy's 13th leader. Turned into a toy by Sugar, he took the form of a cymbal-clapping monkey in a bow tie, sunglasses, striped hat, and pants like his human ones, one of the rare toys whose appearance still hinted at the person beneath.

Sai prizes honesty and fairness, which is why he spoke up for Luffy when the captain faced an unjust disqualification. Deeply emotional, he tends to overreact whenever he turns something down, repeatedly insisting it is unnecessary before growing hostile toward whoever offered it, and he is just as excessive in apology, once dropping to his knees to beg a doctor's forgiveness after already saying sorry three times. He is responsible and protective, swift to hold back his grandfather's rash impulses, devoted to his Hasshoken training, and fiercely loyal to his Happo Army comrades, whose defeats he avenges without mercy. His strong sense of honor extends even to foes, shown when he rushed to stop Baby 5 from taking her own life and shielded her from Pica's attack. Like many in the series, he owns a distinctive laugh: Kakakaka.

Sai, his brother Boo, and his grandfather Chinjao traveled from Kano Country to the Corrida Colosseum, ostensibly to pursue the Mera Mera no Mi but secretly to probe a Donquixote weapons trade. Placed in Block C, Sai defended the disguised Luffy from disqualification, then bristled at being thanked. During the battle royale he downed the Funk Brothers in a single kick to avenge Boo and fought Ideo to a standstill before Luffy knocked him out of the ring. He was later dropped into an underground dungeon, abducted by Trebol, and turned into a toy by Sugar, regaining his human form once Sugar lost consciousness. Joining Luffy's group against Doflamingo's Birdcage, Sai clashed with Baby 5, bent his grandfather's Haki-coated head with a kick to earn the title of Don, and beat the executive Lao G, vowing to marry Baby 5. After the Birdcage fell, he and the other gladiators swore loyalty to the Straw Hats, forming the Grand Fleet. He returned to Kano Country, broke off his engagement to Uholisia, and married Baby 5. At the Levely he reunited with Leo and Rebecca, and the two pirates later flattened the World Noble Charlos when he tried to enslave Shirahoshi, escaping with Mjosgard's aid.