The Umibozu (pronounced "oo-me-boh-zoo"), named after the Umibōzu, a sea monster in Japanese mythology, is a special forces group in the employ of the Japan Maritime Self Defense Force as a black operations unit. The Umibozu have great skill in strategic combat and sniping, as well as all-out assaults. They are infamous in the underworld, and since they don't officially exist, there is no official name for their unit. The unit was infamous in the special forces community for retaking Nemuro, which was occupied by foreign soldiers during WWIV.

When Daisuke Aramaki decided to allow the dismantling of Section 9, in compliance with the 'Special Forces Restriction' bill passed by the government (with the intention of reforming it in secret), the Umibozu were called in to deal with any resistance encountered. They appear to have an extensive arsenal, including attack helicopters. To confront Section 9, they are also equipped with a handful of JMSDF Type 303 powered exoskeletons—large, heavily armored combat suits capable of resisting great amounts of damage and variously armed with machine cannons and grenade launchers. They bear a striking resemblance (Waldo-like arm interfaces, squat head and shoulders, etc) to another Masamune Shirow product, Appleseed's Landmates. These 'armed suits' are impervious to virtually all of Section 9's armaments, and are also equipped with their own thermoptic camouflage systems, making them exceptionally dangerous combatants.

The Umibozu makes a minor appearance after participating in a military exercise in the Niihama refugee camp in 2nd GIG.