|“||Hello. I'm Light Cruiser Ooi. Pleased to make your acquaintance.||„|
Ōi (大井?) was the fourth of five Kuma-class light cruiser, which served in the Imperial Japanese Navy during World War II. She was named after the Ōi River in Shizuoka prefecture, Japan.
Both Kitakami and Ooi share the same 3 forms. Ooi herself has long brown hair.
She is a Boisterous Bruiser who loves battles and bragging about her torpedoes. She is also best friends with Kitakami. She Often referred to as "Ooi-cchi" by Kitakami. Sometimes depicted as extremely Kitakami-sexual.
In the anime Ooi is characterized by being nice and sweet to Kitakami... and rude to everyone who isn't Kitakami, to the point where any and every interruption to the time they spend together is considered a grave offense (case in point: in episode 7, she got angry at a rain squall, which is a natural phenomenon). She joins Mobile Unit Five along with Kitakami in the wake of the fleet reorganization.
- After being remodeled into torpedo cruisers, Ooi, Kitakami, and Kiso can utilize the use of Type A Kou-hyouteki to fire opening torpedoes before shelling phase.
- Her name is from "Ōi river" in Shizuoka prefecture, Japan, literally means "Big Well".
- Torpedoed by USS Flasher 570 nmi (1,060 km; 660 mi) south of Hong Kong, South China Sea at 13°12′N 114°52′E, 19 July 1944.