Goemon Ōi serves as an older brother figure in his social circle after recently relocating to the area. He dispenses advice, particularly to Cota Coga, using a distinctive kabuki tone while maintaining a consistently relaxed demeanor.

Visually, he sports curly hair transitioning from dark green and brown to light green. His attire includes a green and white jacket layered over a black shirt, paired with baggy purple shorts and flip-flops, emphasizing his casual style.

In bottle battles, he specializes in sniping competitions. His primary Bottleman partner is the control-type Gyokurock, aligning with his precision-focused approach during matches.

The character's name draws from Japanese beverage brands: "Ōi" references Ōi Ocha green tea, while "Goemon" connects to the Iemon green tea line, following the series' edible-themed naming pattern.