The swords from this period called Chokuto, had no curvature and were straight swords. The chokuto were very similar to the Chinese and Korean swords used during this same time period. During the 9th century (Late Heian era) the origins of the curved blades came into effect. By the 12th century (mid-Kamakura era) the Samurai class carried Daisho - two samurai swords (katana and wakizashi) which had thicker blades, less tapering towards the point and had ample convex curvature. The 14th century (late Nanbokucho - early Muromachi) produced many kinds of Kodachi and Tanto which were used to emulate Katana or Tachi swords.
Juyo Bunkazai Nagamaki Naoshi, attributed to Bizen Osafune Nagamori
| Class: | Juyo Token |
| Type: | Nagamaki-naoshi katana |
| Mei: | Mumei (o-suriage) |
| Period: | Nambokucho |
| Length: | 66.2 cm |
| Province: | Bizen |
| Sori: | 1.5 cm |
| Moto-kasane: | 0.7 cm |
| Saki-kasane: | 0.5 cm |
| Sugata: | Nagamaki-naoshi shobu-zukuri, iori-mune, moderate torii-zori |
| Nakago: | O-suriage, kiri-jiri, kiri-yasuri, two mekugi-ana, slight sori, length: 14 cm |
| Ji-hada: | Itame mixed with mokume, chikei |
| Hamon: | Choji-midare, nioi-deki, kinsuji, ashi |
This nagamaki-naoshi katana is attributed to Nagamori, a Bizen Osafune smith whose dated blades begin with the third year of Jowa (1347) and extended over a period of roughly 35 years. Nagamori, the son of Nagashige, traditionally was thought to be a student of Chogi, one of the Ten Brilliant Pupils of Masamune. But recent study of his dated swords indicates he worked earlier, and though his relationship with Chogi remains unclear, he would have been about the age of an elder brother. One of Nagamori's nagamaki-naoshi katana has been designated Juyo Bunkaza i (important Cultural Property) by the Japanese Government.