Hatsumi Usuzumi is a third-year student at Eisui Girls' High School in Kagoshima Prefecture and a supporting character in the manga "Saki". She and the other members of Eisui's team are shrine maidens; she belongs to a branch family of the maidens' lineage on the volcanic island Akusekijima, part of the Ryukyu Islands. Hatsumi ended her match segment in the qualifying tournament with a direct yakuman against one of her opponents, winning Eisui the prefectural title and a berth in the national tournament without having teammate Kasumi Iwato play the captain's segment. She is often seen with a ceremonial shaman's mask prior to and following her segment. She has been seen breathing flames from her headdress, which is a Boze mask she may use when performing her duties as an Akuseki shrine maiden.
She can be quite stubborn, still believing that she can make a hand while in the north seat after she was repeatedly blocked by Sae Usuzawa and warned by her teammates. She seems to care a lot about Komaki's well being as she doesn't want Komaki to overexert herself. Hatsumi loves to swim.

When Hatsumi sits in the north seat during her match, the north wind and east wind tiles become attracted to her. When this part of her hand is completed, she will also draw in the south wind and west wind tiles, completing a four-wind yakuman hand. Each north–east and south–west pair is nicknamed the "gate of evil", it refers to the misfortune hailing from the north and east., thus the four-wind hand becomes the "double gates of evil".