What is Kaifu-to in Japanese Katana terminology?

"""Kaifu-to"" (海部刀) refers to the local swords that were made in the Kaifu district of Awa Province, specifically in the area around present-day Kaiyo Town in Kaifu District, Tokushima Prefecture. These swords are characterized by their ""Katakiriba-zukuri"" construction, where one side of the blade is flat and the other side has a ridge, and the spine (Mune) of the sword is serrated like a saw.

The serrated spine is said to have been used to cut ropes and other ship equipment on board, making these swords highly valued by the Awa naval forces.

During the Koto period, these swords were made in the Yamato, Yamashiro, and Soshu traditions, with a focus on ""Honzukuri"" (ridge construction). Later, a large number of ""Wakizashi"" (short swords) with ""Katakiriba-zukuri"" construction were mass-produced. The steel used for these swords often has a visible grain pattern, with large grains mixed in. Some swords also have a straight grain pattern (Masame-hada) mixed with large grains, and there are works with a straight temper line (Suguha) with a wavy pattern (Notare) and a ""Hitotsu no me"" pattern.

One of the most famous Kaifu-to is the ""Iwakiri Kaifu"", which was owned by the Sengoku warlord ""Miyoshi Nagayoshi"" and later passed down to the Fukuoka feudal lord, the ""Kuroda family"". This sword is also listed in the ""Kyoho Meibutsu Cho"" (Kyoho Famous Sword List), and its name is derived from the fact that it was used to cut a rock."